Water – the Most Anomalous Liquid

13 Oct 2014, 09:00 → 7 Nov 2014, 18:00 Europe/Stockholm

132:028 (Nordita, Stockholm)

Anders Nilsson (SLAC and Stockholm University), Lars G. M. Pettersson (Stockholm University), Richard H. Henchman (University of Manchester)

Venue

Nordita, Stockholm, Sweden

Scope

Water is ubiquitous and a prerequisite to life as we know it, yet the fundamental origin in terms of structure and dynamics of its many anomalous properties is still under debate. No simulation model is currently able to reproduce these properties throughout the phase diagram. Experimental techniques, such as x-ray spectroscopies and x-ray and neutron scattering, femtosecond pump-probe and free-electron laser experiments in “no man’s land”, provide data that stimulate new theory developments. This program brings together experimentalists and theoreticians in strong synergy to explore interpretations and to provide a strong basis for further experimental and theoretical advances towards a unified picture of water.

The first goal of the program is to identify critical aspects of water’s anomalous behavior that need to be included in new water models in order to give an overall encompassing agreement with experiments. The second goal is to stimulate further developments of models that can also include perturbations due to ion solvation, hydrophobic interactions as well as describe water at interfaces. There currently exist many water models that can describe some properties well, whereas others are poorly represented. In order to have a fundamental understanding of the relationship between thermodynamic, kinetic and chemical properties with the structure and dynamics of water at various state points and in aqueous solutions it is essential to develop a unified description. The program is intended to stimulate a systematic and synergistic approach towards this goal.

[Timetable]

Format

The program will be built around working groups (WG) during weeks 1, 3 and 4 together with an international conference during week 2. There will be four WGs running each week covering different themes. The 1st week will focus on the anomalous properties of water with an emphasis on simulations, the 2nd week will be an international conference, the 3rd week will focus on theoretical description and our fundamental understanding of various experimental techniques to probe the structure, dynamics and thermodynamics of water. The 4th week will extend water models into ion solvation, hydrophobic interactions and interfaces. The format of the working weeks 1,2 and 4 will be a flexible division into working groups where each group has the task to contribute to, and coauthor, a major review summarizing the current state of the art. Each working group will identify areas where agreement has been reached, areas that are contentious and also provide suggestions for new experiments or theoretical developments to resolve the outstanding issues.

Weeks 1, 3 and 4 will have the following general structure:

Monday: WG chairs present their thoughts on topics to discuss and work on during the week. General discussion and first meeting of working groups.

Tuesday-Friday:Each invited speaker will give a half hour presentation followed by discussion. In addition there will be WG sessions to discuss specific topics and work on writing for the review paper. 16:30- General assembly with reports from each WG and general discussion.

Week 1: Thermodynamics and Simulations of Water
Working group	Topic	WG Chair
WG 1	Thermodynamics of Water	Mikhail Anisimov
WG 2	Force Field Simulations	Francesco Paesani
WG 3	Ab Initio Simulations	Marivi Fernández-Serra
WG 4	Quantum Effects	Tom Markland
Week 2: International Conference - See Below
Week 3: Theoretical Interpretations of Experimental Data
Working group	Topic	WG Chair
WG 5	X-ray Spectroscopy	Jan-Erik Rubensson
WG 6	X-ray and Neutron Scattering	Marie-Claire Bellissent-Funel
WG 7	Vibrational Spectroscopy and Dynamics	Fivos Perakis/Yuki Nagata
WG 8	Confined Water as Model of Supercooled Water	Jan Swenson
Week 4: Aqueous Solutions and Interfaces
Working group	Topic	WG Chair
WG 9	Cations and Anions in Solution	Huib Bakker/Nico van der Vegt
WG 10	Protons and Hydroxide Ions	Ali Hassanali
WG 11	Biomolecular Hydration	Angel Garcia
WG 12	Water at Interfaces	Hendrik Bluhm

Week 2: Confirmed Invited Conference Speakers

Heather Allen, Ohio State University, USA Austen Angell, Arizona State University, USA Mikhail Anisimov, University of Maryland, USA Chris Benmore, Argonne National Laboratory, USA Mischa Bonn, MPI Mainz, Germany Fabio Bruni, Roma 3, Italy Roberto Car, Princeton University, USA Frédéric Caupin, Université de Lyon, France Thomas Elsaesser, Max-Born-Institut Berlin, Germany Giulia Galli, University of Chicago, USA Paola Gallo, Roma 3, Italy Peter Hamm, University of Zurich, Switzerland Yoshihisa Harada, University of Tokyo, Japan Thomas Kühne, Universität Paderborn, Germany David Limmer, Princeton University, USA Thomas Loerting, University of Innsbruck, Austria Francesco Mallamace, Universitá di Messina, Italy Angelos Michaelides, UC London, UK Iwao Ohmine, Institute for Molecular Science, Japan Francesco Paesani, UC San Diego, USA Athanassios Panagiotopoulos, Princeton University, USA John Rehr, University of Washington, USA Jonas Sellberg, Stockholm University, Sweden James Skinner, UW Madison, USA Gene Stanley, University of Boston, USA Jan Swenson, Chalmers University of Technology, Sweden Hajime Tanaka, Tokyo University, Japan Renato Torre, University of Firenze, Italy Carlos Vega, Universidad Complutense Madrid, Spain Limei Xu, Peking University, China

Application

If you want to apply for participation in the program, please fill in the application form. You will be informed by the organizers shortly after the application deadline whether your application has been approved. Due to space restrictions, the total number of participants is strictly limited. (Invited speakers and WG chairs are of course automatically approved, but need to register anyway.)

Application deadline: 31 August 2014

A minimum stay of one working week is required and we encourage participants to stay for a period of at least two weeks.

There is no registration fee.

Travel Reimbursement

Invited speakers and WG chairs will have their travel expenses reimbursed by the program. Limited travel grants are available to participants in the program. If you are interested in such a grant, please mark the corresponding field in the application form, briefly summarize your interest in the program in the comments field, and indicate an estimation of your expected travel expenses. Since only a limited number of grants is available, decision concerning the grants will be made on a case-by-case basis and you will be notified shortly after the application deadline.

Accommodation

Nordita provides a limited number of rooms in the Stockholm apartment hotel BizApartments free of charge for accepted program participants.

Sponsored by:

The Royal Swedish Academy of Sciences through its Nobel Institutes for Physics and Chemistry

Week 1 Group Photo Week_1.JPG

Week 2 Group Photo Week_2.JPG

Week 3 Group Photo Week_3.JPG

Week 4 Group Photo Week_4.JPG

Monday 13 October

1 Welcome

pictures Group_Photo1.JPG Group_Photo2.JPG

2 Mikhail Anisimov

10:00 Discussion

10:15 break

3 Francesco Paesani

11:30 Discussion

11:45 Lunch

4 Marivi Fernandez-Serra

13:45 Discussion

5 Tom Markland

14:45 Discussion

15:00 break

15:30 Working Group Discussions

Tuesday 14 October

6 Charusita Chakravarty

7 Sotiris Xantheas

8 Joost VandeVondele

10:30 break

9 Michele Ceriotti

10 Limei Xu

11 Andrés Cisneros

12:30 Lunch

13:30 Working Group Discussions

15:00 break

15:30 Working Group Discussions

16:30 Summary of Discussions

Wednesday 15 October

12 Michael Gillan

13 Peter Kusalik

14 Paola Gallo

10:30 break

11:00 Writing Outline

11:30 Writing in Working Groups

12:30 Lunch

13:15 Excursion to the Wasa Museum

Thursday 16 October

15 Lars Ojamäe

16 Jose M. Soler

17 Ross McKenzie

10:30 break

18 Jibao Lu

19 Albert Bartok-Partay

20 Miguel Morales

12:30 Lunch

13:30 Writing in Working Groups

15:00 break

15:30 Writing in Working Groups

16:30 Summary of Discussions and Writing

Friday 17 October

21 C. Austen Angell

22 Thor Wikfeldt

10:00 break

10:30 Writing in Working Groups

12:30 Lunch

13:30 Discussion and Summary of the Week

Monday 20 October

23 Opening of the Conference by Katie Freese

24 Metastable Water: the Schism (Empiricists vs Modelers), and a Possible Resolution

The bizarre behavior of water in its low pressure, supercooled, domain is now well known. Unless confined nanoscopically, response functions and transport properties follow power laws in T that are characteristic of approach to spinodal limits on phase stability. Such behavior has provoked a great deal of computer simulation-based investigation, key results of which turn out to be in stark conflict with the predictions of empirical (engineering) equations of state when extrapolated into the domain of isotropic tension (negative pressure). This domain is the least investigated in all of water research, despite the abundance, in nature, of samples for study (milky quartz, under the microscope). We posit that the secrets of water lurk on the other side of the zero pressure line. In this talk I compare some of the predictions of currently favored pair potential simulation models with the best available data for real water, in both positive and negative pressure domains. We first apply an approach that is well- tested for models with critical points, to the best available positive pressure equation of state, but fail to find the isochore-crossing "smoking gun" anywhere in the positive pressure domain. Only spinodal divergences are indicated, and the value at ambient pressure coincides with the limit of supercooling from recent short time μdroplet studies. Spinodals without critical points at positive pressure, imply an L-L coexistence line at positive pressures, rather than a LLCP. Turning to isobaric data, we show how models that are in good accord with experiment at normal temperatures deviate dramatically at large supercooling. While TMDs from certain models agree quite well with experiment at positive pressure, for P < -100 MPa, they vary in opposite directions1. However, all leading empirical equations of state, (based on positive pressure data) accord with the direct observations - implying that any critical point has merged with the gas- liquid spinodal. Heat capacity data are especially valuable because of availability over wide temperature ranges (including near Tg) and also from very fast measurements that postpone crystallization while yielding faster structural relaxation data. We compare them with thermodynamic constructions to argue that a first order transition near 230K provides the most plausible rationalization. Finally, we introduce new data from non-crystallizing water- rich solutions of a previously unstudied class. Discovered as an offshoot of protein folding studies, these are aqueous solutions of hydrazinium salts that, according to melting point depression data, dissolve to form ideal solutions. At 15 mole% salt they yield cooling thermograms with large endothermic spikes. These mimic the diverging heat capacity of pure water but are not interrupted by crystallization (perhaps due to a sort of wall-free confinement). This allows both sides of the anomaly to be seen before the glass transition intercedes. We will report new TMD data to argue that these spikes are the manifestation of the first order liquid-liquid transition that would occur in water if crystallization did not intercede. A phase diagram from the H-bond-modified van der Waals thermodynamic model of Peter Poole, provides a simple rationalization for all of these observations. [1] Meadley, S. L. & Angell, C. A. Water and its closest relatives: insights from metastable state studies. Nuovo Cimento, Enrico Fermi summer school on water (in press) arXiv 1404.4031 (2014).

Speaker: Prof. C. Austen Angell (Arizona State University)

10:10 break

25 Could Dynamics of Supercooled Water be Explained by Peculiar Thermodynamics?

Properties of supercooled water exhibit spectacular anomalies which have been a subject of debates for decades [1]. Twenty years ago Poole et al. suggested that the anomalous properties of supercooled water may be caused by a critical point that terminates a line of metastable (and hidden below the line of homogeneous ice nucleation) liquid-liquid separation of lower-density and higher-density water [2]. This phenomenon can be viewed as “water’s polyamorphism”. Most recent accurate simulations of the ST2 model of water favor the existence of this metastable transition [3]. A phenomenological model, in which liquid water at low temperatures is considered as a “solution” of two hydrogen- bond network structures with different entropies and densities explains why supercooled water may unmix and nicely describes the thermodynamic anomalies in supercooled water [4] and in the popular water-like models, mW and ST2 [5,6]. The existence of two alternative structures in water may [6] or may not [5] result in the liquid-liquid separation, depending on the nonideality of mixing of these structures. The two-state thermodynamics has been recently generalized to aqueous solutions for describing the liquid-liquid transitions stemming from the hidden liquid-liquid transition in pure water [7]. In supercooled water, anomalies in dynamics closely follow the thermodynamics anomalies. However, contrary to the vapor-liquid transitions, the anomalies in supercooled water have been attributed to a structural relaxation [8]. While the dispersion of sound near the vapor-liquid critical point is solely an effect of the relaxation of critical density fluctuations, the dispersion of sound in supercooled water is most likely a viscoelastic relaxation phenomenon [9]. Coupling between the viscoelastic structural relaxation and a diffusive decay of density fluctuations could be an important factor in understanding the supercooled-water dynamics. Moreover, supercooled water fundamentally differs from water in the vapor-liquid critical region due to a non- conserved nature of the order parameter associated with the orientation of hydrogen bonds in water [10]. Phenomenologically, this order parameter can be viewed as the extent of “reaction” between two alternative structures of water [7]. Rather than obeying the diffusive space-dependent decay, the relaxation of the non-conserved order parameter is independent of the wave number. This would have far- reaching implications for various dynamic properties of supercooled water. 1. Angell, C. A., Supercooled water, in Water: A comprehensive treatise. Vol. 7, Ed. Franks, F. Plenum Press, New York, 1982, 215-338. 2. Poole, P.H.; Sciortino, F.; Essman, U.; Stanley, H. E., Phase behavior of metastable water. Nature 1992, 360, 324-328. 3. Palmer, J. C.; Martelli, F.; Liu. Y.; Car, R.; Panagiotopoulos, A. Z.; Debenedetti, P. G., Metastable liquid– liquid transition in a molecular model of water. Nature 2014, 510, 385-388. 4. Holten, V.; Anisimov, M. A., Entropy driven liquid–liquid separation in supercooled water. Sci. Rep. 2012, 2, 713/1- 713/6; supplement: www.nature.com/scientificreports. 5. Holten, V.; Limmer, D. T.; Molinero, V.; Anisimov, M. A., Nature of the anomalies in the supercooled liquid state of the mW model of water. J. Chem. Phys. 2013, 138, 174501/1- 174501/10. 6. Holten, V.; Palmer, J. C.; Poole, P. H.; Debenedetti, P. G.; Anisimov, M. A., Two-state thermodynamics of the ST2 model for supercooled water”. J. Chem. Phys. 2014, 140, 104502/1- 104502/13. 7. Biddle Biddle, J. W., Holten, V.; Anisimov, M. A., Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water. J. Chem. Phys. 2014, 141, 074504/1-074504/10. 8. Mallamace, F.; Corsaro, C.; Stanley, H. E., Possible relation of water structural relaxation to water anomalies. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 4893-4904. 9. Cunsolo, A.; Nardone, M., Velocity dispersion and viscous relaxation in supercooled water. J. Chem. Phys. 1996, 105, 3911/1-3911/17. 10. Tanaka, H., Importance of many-body orientational correlations in the physical description of liquids. Faraday Discussions 2013, 167, 9-76.

Speaker: Prof. Mikhail Anisimov (University of Maryland)

26 Metastable Liquid-Liquid Transition in the ST2 Model for Water

I plan to discuss results on the liquid–liquid transition in the ST2 model of water recently obtained by Palmer et al. [Nature 510: 385 (2014)]. Six advanced sampling methods were used to compute the free-energy surface, which shows that two metastable liquids and a stable crystal exist at the same deeply supercooled thermodynamic condition. The transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. These findings provide unambiguous evidence for a liquid–liquid transition in the ST2 model of water, and point to the separation of time scales between crystallization and relaxation as being crucial for enabling it.

Speaker: Prof. Athanassios Panagiotopoulos (Princeton University)

12:30 Lunch

27 Liquid Water, the Most Complex Fluid: New Results in Nanoconfined and Biological Environments

We will introduce some of the 64 anomalies of the most complex of liquids, water — focusing on recent progress in understanding these anomalies by combining information provided by recent spectroscopy experiments (and simulations) on water in bulk, nanoconfined and biological environments [1]. We will interpret evidence from recent experiments designed to test the hypothesis that liquid water has behavior consistent with the hypothesized “liquid polymorphism” in that water might exist in two different phases [2–5]. We will also discuss recent work on nanoconfined water anomalies as well as the apparently related, and highly unusual, behavior of water in biological environments [6–8]. Finally, we will discuss how the general concept of liquid polymorphism is proving useful in understanding anomalies in other liquids, such as silicon, silica [9], and carbon, as well as metallic glasses, which have in common that they are characterized by two characteristic length scales in their interactions. This work has been generously supported by the NSF Chemistry Division and was performed in close collaboration with a number of colleagues. In addition to the co-authors listed above, these include D. Corradini, P. G. Debenedetti, G. Franzese, P. Kumar, J. Luo, M. G. Mazza, O. Mishima, P. H. Poole, P. J. Rossky, S. Sastry, D. Schlesinger, F. Sciortino, K. C. Stokely, and M. Yamada. [1] H. E. Stanley, ed., Liquid Polymorphism [Vol. 152 in the series Advances in Chemical Physics], S. A. Rice, series editor (Wiley, New York, 2013). [2] T. A. Kesselring, E. Lascaris, G. Franzese, S. V. Buldyrev, H. J. Herrmann, and H. E. Stanley, “Finite-Size Scaling Investigation of the Liquid-Liquid Critical Point in ST2 Water and its Stability with Respect to Crystallization,” J. Chem. Phys. 138, 244506 (2013). [3] F. Mallamace, C. Corsaro, S.-H. Chen, and H. E. Stanley, “Transport and Dynamics in Supercooled Confined Water,” Advances in Chemical Physics 152, 203–262 (2013). [4] P. Kumar, K. T. Wikfeldt, D. Schlesinger, L. G. M. Pettersson, and H. E. Stanley, “The Boson Peak in Supercooled Water,” Nature Scientific Reports 3, 1980 (2013). [5] P. Kumar and H. E. Stanley, “Thermal Conductivity Minimum: A New Water Anomaly,” J. Phys. Chem. 115, 14269–14273 (2011). [6] F. Mallamace, C. Corsaro, D. Mallamace, H. E. Stanley, and S.-H. Chen, “Water and Biological Macromolecules,” Advances in Chemical Physics 152, 263–308 (2013). [7] S. Sharma, S. K. Kumar, S. V. Buldyrev, P. G. Debenedetti, P. Rossky, and H. E. Stanley, “A Coarse-Grained Protein Model in a Water-Like Solvent,” Nature Scientific Reports 3, 1841 (2013). [8] F. Mallamace, C. Corsaro, D. Mallamace, P. Baglioni, H. E. Stanley, and S.-H. Chen, “A Possible Role of Water in the Protein Folding Process,” J. Phys. Chem. B 115, 14280–14294 (2011). [9] E. Lascaris, M. Hemmati, S. V. Buldyrev, H. E. Stanley, and C. A. Angell, “Search for the Liquid-Liquid Critical Point in Models of Silica,” J. Chem. Phys. 140, 224502 (2014).

Speaker: Prof. Gene Stanley (Boston University)

28 Water Dynamics, Fluctuations and Phase Transitions

Water is the most ubiquitous substance on earth and known to have anomalous properties, arisen from the characteristic structure and dynamics of hydrogen bond network in water. There exist intermittent collective molecular motions associated with the rearrangement of the hydrogen bond network and concomitant fluctuation and relaxation in liquid water. Two aspects of the water dynamics will be discussed; (1) Water dynamics in the low temperatures, 2) (2) Molecular dynamical mechanism of freezing3) and melting of water, Upon cooling, water freezes into ice. This process is a most familiar phase-transition, occurring in many places in nature, but is extremly hard to be simulated by a computer simulation. Since the global potential energy surface of HBN rearrangement is rugged and complex, water is much harder to freeze than simple liquid We will discuss how an initial nucleus is created and grows on the rugged potential energy surface of water and the role of fluctuation in the freezing process. Resilient hydrogen bonds render ice melting complex. A key step to break the resilient hydrogen bonds of ice is not the formation but rather the spatial separation of defect pairs. We find that once it is separated, the defect pair—either an interstitial (I) and a vacancy (V) defect pair (a Frenkel pair), or an L and a D defect pair (a Bjerrum pair)9—is entropically stabilized, or ‘entangled’. In this state, defects with threefold hydrogen-bond coordination persist and grow, and thereby prepare the system for subsequent rapid melting. We carry out extensive molecular dynamics simulations from room temperatures down to as low as 130K, without attaining the freezing to ice. Relaxation time is found to vary over twelve orders of magnitude in traversing this range, with occurrence of multiple anomalies. Structural, dynamical and thermodynamic properties all show a crossover, around 220K, to a different, low density liquid state with different dynamical properties. On further cooling, this low density liquid again undergoes a dynamical transition around 197K region where (i) the density reaches its minimum (ii) the dynamical heterogeneity starts to decrease after reaching maximum. The temperature dependence of relaxation times reveals three distinct branches, with discontinuities around 220 K and 197K. Molecular pictures of the dynamics in theses three branches will be discussed.

Speaker: Prof. Iwao Ohmine (Institute for Molecular Science, Myodaiji, Okazaki)

15:30 break

29 Recent Measurements on Bulk Supercooled Water: Equation of State at Negative Pressure, and Viscosity at Positive Pressure

The origin of water anomalies is an elusive mystery, but recent experiments on supercooled water have revived the hope to unravel it. For instance, surface tension has been measured down to -25°C [1], and the structure factor of micron-sized water droplets analyzed down to -44°C [2]. We will review our recent work on metastable water. We have used water inclusions in quartz crystals to reach negative pressures in the -100 MPa range [3]. Brillouin light scattering reveals anomalies in the sound velocity of water, especially in the doubly metastable region where water is both supercooled and under mechanical tension [4]. The new data allows to construct an equation of state for water at negative pressure [5]. The line of density maxima is determined down to -120 MPa. Furthermore, extrema in thermodynamic responses functions are detected. We will also describe another set of experiments to measure the viscosity of supercooled water at ambient and positive pressure [6]. [1] Hruby J. et al., J. Phys. Chem. Lett. 5, 425-428 (2014). [2] Sellberg J. et al., Nature 510, 381-384 (2014). [3] El Mekki Azouzi M., Ramboz C., Lenain J.-F. and Caupin F., Nature Physics 9, 38-41 (2013). [4] Pallares G et al., Proc. Natl. Acad. Sci. USA 111, 7936-7941 (2014). [5] Pallares G et al., in preparation. [6] Dehaoui A., Singh L.P., Issenmann B., and Caupin F., in preparation.

Speaker: Prof. Frédéric Caupin (Université de Lyon and Institut Universitaire de France)

30 On the Fluctuations that Order and that Frustrate Liquid Water

At ambient conditions, water sits close to phase coexistence with its crystal. More so than in many other materials, this fact is manifested in the fluctuations that maintain a large degree of local order in the liquid. These fluctuations and how they result in long-ranged order, or its absence, are emergent features of many interacting molecules. Their study therefore requires using the tools of statistical mechanics for their systematic understanding. In this talk I present an overview such an understanding. In particular, I focus on collective behavior that emerges in liquid and solid water. At room temperatures, the thermophysical properties of water are quantified and rationalized with simple molecular models. A key feature of these models is the correct characterization of the competition between entropic forces of packing and the energetic preference for tetrahedral order. At cold temperatures, the properties of ice surfaces are studied with statistical field theory. The theory I develop for the long wavelength features of ice interfaces allows us to explain the existence of a premelting layer, the stability of ice in confinement and the dynamical fragile-to-strong crossover observed in confined water. In between these extremes, the dynamics of supercooled water are considered. A detailed theory for the early stages of coarsening is developed and used to explain the peculiar observation of a transient second liquid state of water. When coarsening dynamics are arrested, the result is the formation of glassy states of water. I show that out-of-equilibrium the phase diagram for supercooled water exhibits a rich amount of structure, including a triple point between two glass phases of water and the liquid. Using this perspective a number of response properties of amorphous ice are calculated and compared with experiment. Throughout all of this work, by invoking only behaviors that are well established and universal to many other liquids, I show how the properties of water can be understood without having to hypothesize the existence of extra features of water's phase diagram.

Speaker: Dr David Limmer (Princeton University)

Tuesday 21 October

31 Structure and Dynamics of Interfacial Water

At the surface or interface of water, the water hydrogen-bonded network is abruptly interrupted, conferring properties on interfacial water different from bulk water. Owing to its importance for disciplines such as electrochemistry, atmospheric chemistry and membrane biophysics, the structure of interfacial water has received much attention. We elucidate the structure and structural dynamics of interfacial water using ultrafast surface-specific sum-frequency generation (SFG) vibrational spectroscopy. Specifically, for the water-air interface, we find that the interface is both structurally heterogeneous [1] and highly dynamical [2,3]. We reveal the nature of the heterogeneity, find surprisingly rapid inter- and intramolecular energy transfer processes and quantify the reorientational dynamics of interfacial water. At the water-mineral interface, we report a dramatic effect of flow of water along the mineral surface on the organization of water at the interface [4]. [1] Hsieh, C.S.; Okuno, M.; Backus, E. H. G.; Hunger, J.; Nagata, Y.; Bonn, M.. Angew. Chem.-Intern. Ed. 2014, 31, 8146 (VIP paper). [2] Hsieh, C. S.; Campen, R. K.; M. Okuno; E. H. G. Backus; Y. Nagata; and M. Bonn, Proc. Nat. Acad. Sci. USA 2013, 110, 18780. [3] Piatkowski, L.; Zhang, Z.; Backus, E. H. G.; Bakker, H.J.; Bonn, M., Nature Commun. 2014, 5, 4083. [4] Lis, D.; Backus, E. H. G.; Hunger, J.; Parekh, S. H.; Bonn, M., Science 2014, 344, 1138.

Speaker: Prof. Mischa Bonn (Max Planck Institute for Polymer Research)

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10:00 break

32 The Air-Water Interface: As Influenced by Ions, Lipids, and Electric Fields

The air-water interface has been the focus of research in the Allen Lab at Ohio State for more than a decade. We utilize nonlinear and linear optical spectroscopic methods to understand the local intermolecular interactions and organization of water itself with various solutes and monolayers. Motivated by atmospheric aerosol chemistry of marine and urban regions, and biophysical applications related to lung lining and biomembranes, monovalent and divalent cations and anions continue to be investigated by our group using conventional and heterodyne-detection vibrational sum frequency generation (VSFG) spectroscopy. Interest is in the surface propensity and availability for reaction at water surfaces. Ion valency, polarizability, size, shape, and identity of the counterion are critical factors in considering ion organization and subsequent changes in interfacial electric field at the air water interface. The hydrating water molecules play a key role in the interfacial organization of other species in the solution, and is studied directly as it reveals the details of ion interfacial distributions. Phospholipids and fatty acids are also investigated using both VSFG and Brewster angle microscopy (BAM). Head group differences, especially with regard to hydrogen bonding capability and extent, are discerning factors for surface organization and shape distinction at the water surface.

Speaker: Prof. Heather Allen (Ohio State University)

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33 Structure and Dynamics of Water at Surfaces

Water/solid interfaces are relevant to a broad range of physicochemical phenomena and technological processes such as corrosion, lubrication, heterogeneous catalysis and electrochemistry (Nature Mater 11, 667 (2012)). In this talk some of our recent work in this area will be covered. Specifically results on water droplet diffusion on the surfaces of layered materials will be presented and a novel “surfing” mechanism for droplet diffusion discussed. In addition, simulations of ice nucleation on various nanoparticles with different physiochemical characteristics will be presented and the fundamental insight obtained from these into heterogeneous ice nucleation discussed. Time permitting some recent ab initio molecular dynamics results at wet interfaces in which rapid proton transfer is observed will also be discussed.

Speaker: Prof. Angelos Michaelides (University College London)

12:30 Lunch

34 Coarse Graining Electrons”: Many-Body Water Potential for Simulations from the Gas to the Condensed Phase

Two of the most challenging problems at the frontier of contemporary electronic structure theory are the accurate representation of intermolecular interactions and the development of reduced-scaling algorithms applicable to large systems. To some extent, these two problems are antithetical, since the accurate calculation of non- covalent interactions typically requires correlated, post-Hartree– Fock methods whose computational scaling with respect to system size precludes the application to large systems. In this talk, I describe our theoretical/computational framework (MB- pol) for the development of chemically accurate and transferable intermolecular potentials derived entirely from “first principles”. MB-pol potentials are built upon the many- body expansion of molecular interactions with explicit 2-body and 3-body terms represented by high-degree invariant polynomials obtained from application of machine learning techniques to CCSD(T)/CBS reference data. These terms smoothly transition at intermediate range into a sum of electrostatic and dispersion interactions that reproduce the correct asymptotic behavior. The induction contributions to non-pairwise additive interactions are taken into account using polarizable point dipoles. The accuracy of the MB- pol approach is assessed here through the analysis of the properties of water from the gas to the condensed phase with a particular emphasis on nuclear quantum effects and vibrational spectroscopy.

Speaker: Prof. Francesco Paesani (University of California, San Diego)

35 Freezing of Water from Computer Simulations: Thermodynamic and Kinetic Aspects

Among all the freezing transitions, that of water into ice is probably the most relevant to biology, physics, geology or atmospheric science. Computer simulations can be used to locate the coexistence conditions for a certain water model. Two procedures can be used to locate the coexistence. In the first one free energy calculations must be performed for the fluid and solid phases to locate the coexistence point. Although the free energy of the fluid phase can be determined easily, for the solid phase one must use special methods as for instance the Einstein crystal method. In this work we shall illustrate how to perform free energy calculations for the solid phases of water (ices) using a Molecular Dynamics package as GROMACS [1]. The second route to phase equilibrium is the direct coexistence method, where the two coexistence phases are located within the same simulation box. We shall present results illustrating that the direct coexistence method is efficient, not only for ice Ih, but for the rest of high pressure polymorphs of water. Besides we shall discuss two issues related to the use of direct coexistence simulations: its stochastic character [2] and in the particular case of water the subtle issue of the proton ordering of ices (with no disorder, partial disorder or complete disorder) [3]. The direct coexistence method can also be used to analyze the melting point of finite size clusters of ice embedded within a supercooled sample of liquid water. In this way the size of the critical cluster for the homogeneous freezing of water can be evaluated. For temperatures between -15 and -35 degrees below freezing the size of the critical clusters varies from 8000 molecules to 600. The interfacial ice-water free energy can be estimated by using the expression of Classical Nucleation Theory for the size of the critical cluster (we obtained a value of around 29mN/m in good agreement with experimental reported values). After determining the interfacial free energy, the free energy barrier for nucleation of ice can be estimated. The free energy barrier varies from 500kT at -15 Celsius to about 300kT at -20 Celsius. These high barriers strongly suggest that homogeneous ice nucleation is extremely unlikely above -20 Celsius and that freezing above this temperature must be necessarily heterogeneous.[4] The nucleation rate of ice for TIP4P/2005 at the locus of maximum compressibility of supercooled water at room pressure (located on the Widom line) is very small so that the maximum in compressibility in this model can not be attributed to the transient formation of ice [5]. [1] J. L. Aragones, E. G. Noya, C. Valeriani and C. Vega J. Chem. Phys. 139 034104 (2013). [2] J. R. Espinosa and E. Sanz and C. Valeriani and C. Vega J. Chem. Phys. 139 144502 (2013). [3] M. M. Conde and M. A. Gonzalez and J. L. F. Abascal and C. Vega J. Chem. Phys. 139 154505 (2013). [4] E. Sanz and C. Vega and J. R. Espinosa and R. Caballero- Bernal and J.L.F. Abascal and C.Valeriani J. Am. Chem. Soc. 135 15008 (2013). [5] D. T. Limmer and D. Chandler, J. Chem. Phys. 138, 214504 (2013).

Speaker: Prof. Carlos Vega (Universidad Complutense)

15:30 break

36 Electronic and Vibrational Spectroscopy of Aqueous Interfaces from First Principle Calculations

We will discuss recent progress and new challenges in predicting the electronic [1] and vibrational [2] properties of water and simple aqueous solutions [3] interfaced with semiconducting and insulating surfaces. We will present results obtained by coupling ab initio molecular dynamics calculations with many body perturbation theory [4]. [1] T. Anh Pham, Cui Zhang, Eric Schwegler, and Giulia Galli, Phys. Rev. B 89, 060202(R) (2014); T. Anh Pham, Donghwa Lee,Eric Schwegler, and Giulia Galli 2014 (submitted). [2] Quan Wan, Leonardo Spanu, Giulia Galli and Francois Gygi, J. Chem. Theo. Comp. 9, 4124 (2013); Patrick Huang, T. Anh Pham, Giulia Galli, and Eric Schwegler , J. Phys. Chem. C 118, 8944 (2014). [3] Alex P. Gaiduk, Cui Zhang, Francois Gygi, and Giulia Galli, Chem. Phys. Lett. 604, 89 (2014); Quan Wan, Leonardo Spanu, Francois Gygi and Giulia Galli J. Phys. Chem. Lett. 5(15), 2562 (2014); Cui Zhang, Tuan Anh Pham, Francois Gygi and Giulia Galli, J. Chem. Phys- Comm. 138, 181102 (2013). [4] T. Anh Pham, Huy-Viet Nguyen, Dario Rocca and Giulia Galli, Phys. Rev. B 87, 155148 (2013) ; Yuan Ping, Dario Rocca and Giulia Galli, Chem Soc. Rev. 42, 2437 (2013).

Speaker: Prof. Giulia Galli (University of Chicago)

37 Microscopic Properties of Liquid Water from Combined Ab Initio Molecular Dynamics and Energy Decomposition Studies

A new energy decomposition analysis for periodic systems based on absolutely localized molecular orbitals is presented [1, 2]. In combination with the recently developed ”Car-Parrinello-like approach to Born-Oppenheimer MD” [3] this not only allows for ab initio molecular dynamics simulations on previously inaccessible time and length scales, but also provide unprecedented insights into the nature of hydrogen bonding between water molecules. The effectiveness of this new combined approach is demonstrated on liquid water and the water/air interface [4, 5]. Our simulations reveal that although a water molecule forms, on average, two strong donor and two strong acceptor bonds, there is a significant asymmetry in the energy of these contacts. We demonstrate that this asymmetry is a result of small instantaneous distortions of hydrogen bonds and show that the distinct features of the X-ray absorption spectra originate from molecules with high instantaneous asymmetry [1, 2, 6, 7]. [1] T. D. Kuhne and R. Z. Khaliullin, Nature Comm. 4, 1450 (2013). [2] R. Z. Khaliullin and T. D. Kuhne, Phys. Chem. Chem. Phys. 15, 15746 (2013). [3] T. D. Kuhne, M. Krack, F. Mohamed and M. Parrinello, Phys. Rev. Lett. 98, 066401 (2007). [4] T. D. Kuhne, M. Krack and M. Parrinello, J. Chem. Theory Comput. 5, 235 (2009). [5] T. D. Kuhne, T. A. Pascal, E. Kaxiras and Y. Jung, J. Phys. Chem. Lett. 2, 105 (2011). [6] C. Zhang, R. Z. Khaliullin, D. Bovi, L. Guidoni and T. D. Kuhne, J. Chem. Phys. Lett. 4, 3245 (2013) [7] R. Z. Khaliullin and T. D. Kuhne, J. Am. Chem. Soc. 136, 3395 (2014).

Speaker: Prof. Thomas Kuhne (University of Paderborn)

Wednesday 22 October

38 High Energy X-ray Experiments on Water as a Function of Temperature

We present diffraction data that yields the oxygen-oxygen pair distribution function, g_OO (r), over the range -20 to +93 deg.C. The running O-O coordination number, which represents the integral of the pair distribution function as a function of radial distance, is found to exhibit an isosbestic point at 3.30(5)Å. The probability of finding an oxygen atom surrounding another oxygen at this distance is therefore shown to be independent of temperature and corresponds to an O-O coordination number of 4.3(2). Moreover, the experimental data also shows a continuous transition associated with the second peak position in g_OO (r), concomitant with the compressibility minimum at 46.5 deg.C.

Speaker: Dr Chris Benmore (Argonne National Laboratory)

09:30 break

39 Studying Supercooled Water and Ice Using an X-ray Laser

Experiments on pure bulk water below about 235 K have so far been difficult: crystallization occurs very rapidly below the homogeneous nucleation temperature of 232 K and above ~160 K in bulk water, leading to a “no man’s land” devoid of experimental results. In my talk, I will present successful measurements to study the structure of bulk water below 232 K and derive the homogeneous ice nucleation rate. Using femtosecond x-ray pulses generated by the world's first hard x-ray laser to probe evaporatively cooled droplets of supercooled water, we find experimental evidence for the existence of metastable bulk liquid water down to temperatures of 227 K in the previously largely unexplored “no man’s land”. The occurrence of crystallization within the water droplets increased rapidly below 232 K, from which the nucleation rate was derived. We observed a slower rate than anticipated from previous experiments, which can be explained by a rapid decrease in water's diffusivity. These findings are consistent with the proposed "fragile-to-strong" transition expected to occur upon deep supercooling. Finally, I will conclude with an outlook of future experiments on water and ice using x-ray lasers.

Speaker: Dr Jonas Sellberg (Stockholm University)

40 Pushing the Boundaries to "No-Man's Land": Raising the Crystallization Line T_X

Liquid water crystallizes rapidly both below the homogeneous nucleation line T_H and above the crystallization line T_X. The "no-man's land" inbetween T_H and T_X, in which liquid water can only be studied on ultrashort timescales, represents a region, in which the properties of water are largely unknown. It has, thus, been a playground for computer simulations on the nanosecond timescale, which predict contradictory scenarios about water's properties. In our work we have studied the properties of amorphous ices and deeply supercooled water in the vicinity of T_X. By applying different protocols for the preparation of amorphous ices we were able to push the T_X boundary to 5-10 K higher temperatures in the pressure range up to 500 MPa, therebye narrowing the no-man's land and providing access to bulk water's properties in a broader temperature range. Within this temperature range the amorphous ices soften significantly and relaxation times reach the subsecond domain so that they can be regarded as ultraviscous liquids. Analysis of crystallization kinetics suggests that the elimination of nano-crystalline domains in both low- (LDA) and high-density amorphous ices (HDA) is the key to the shift of the T_X line. In the absence of nano-crystalline domains within the glassy matrix crystallization is delayed because one channel leading to crystal growth is essentially suppressed.

Speaker: Prof. Thomas Loerting (University of Innsbruck)

12:00 Lunch

41 2D-Raman-Thz Spectroscopy: A Sensitive Test of Polarizable Water Models

Water is a complex liquid due to the hydrogen-bond network that it forms. The associated low-frequency spectrum of water reports directly on its thermally excited intermolecular degrees of freedom. In this frequency range, the intermolecular spectrum of water consists of broad, almost featureless bands at ~600 cm-1 (hindered rotations), ~200 cm-1 (hydrogen bond stretching) and at ~60 cm-1 (hydrogen bond bending). In order to resolve the lineshape functions of these modes as well as their couplings, a multidimensional spectroscopy directly in this frequency range is needed. I will discuss 2D-Raman-THz spectra of liquid water as one such spectroscopy (see Fig. 1) [1]. In order to facilitate the interpretation of these experiments, all-atom molecular dynamics simulations have been performed with various polarizable models of water. It is found that the 2D- Raman- THz response depends extremely critically on the description of polarizability. From the models which have been tested so far, the best (but certainly not perfect) agreement with experiment is obtained for the TL4P model, which has recently been introduced by Tavan and coworkers [2]. [1] J. Savolainen, S. Ahmed and P. Hamm, “2D-Raman- THz Spectroscopy of Water” Proc. Natl. Acad. Sci. USA, 110 (2013) 20402 [2] P. Tröster, K. Lorenzen, M. Schwörer, and P. Tavan, J. Phys. Chem. B 117, 9486 (2013).

Speaker: Prof. Peter Hamm (University of Zurich)

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42 Hydration of Phospholipids and DNA Studied by Femtosecond Two-Dimensional Infrared Spectroscopy

Phosphate-water interactions play a key role for the structural and functional properties of biomolecular systems such as phospholipid membranes and DNA. Nonlinear vibrational spectroscopy in the femtosecond time domain allows for mapping fluctuating interactions of hydrated phosphate groups and for unraveling the time scale and pathways of vibrational energy flow. Here, we study such processes in DOPC (dioleoylphosphatidylcholine) reverse micelles [1], a phospholipid model system containing small H2O pools of variable size, and in hydrated DNA oligomers [2]. We report the first 2D spectra of phosphate stretching vibrations and other modes in the frequency range from 900 to 1300 cm-1 ([3] and unpublished results). In DOPC reverse micelles, the line shape of the symmetric and asymmetric (PO2)- stretch diagonal peaks displays a pronounced inhomogeneous broadening that persists into the picosecond time domain. A line shape analysis by density matrix theory gives insight into the frequency-time correlation function, revealing two distinct structural dynamics components. The first 300 fs contribution is related to spatial fluctuations of charged phospholipid head groups with additional water contributions at high hydration levels, the second quasistatic component accounts for water−phosphate interaction geometries persisting longer than 10 ps. A similar behavior is observed for the (PO2)- stretch and backbone vibrations of hydrated DNA. In a second series of 2D experiments, we studied the dynamics of OH stretching excitations of the H2O nanopools in DOPC reverse micelles [4]. Average OH stretching lifetimes between 550 and 300 fs are found between w0=1 and 16 (1 and 16 water molecules per phosphate), and coupling to the OH bending mode represents the main decay channel. Vibrational relaxation establishes a hot water ground state with blue-shifted OH stretching absorption that displays a homogeneous lineshape and affects the 2D OH stretch spectra in a wide frequency range. Energy dissipation is faster than structural fluctuations of the water pools for w0=1 to 8. Our results suggest that local pools as small as 3 water molecules interacting with a phosphate head group are sufficient to establish a hot water ground state. [1] N. E. Levinger, R. Costard, E. T. J. Nibbering, T. Elsaesser, “Ultrafast Energy Migration Pathways in Self-Assembled Phospholipids Interacting with Confined Water”, J. Phys. Chem. A 115, 11952-11959 (2011). [2] M. Yang, Ł. Szyc, T. Elsaesser, “Decelerated Water Dynamics and Vibrational Couplings of Hydrated DNA Mapped by Two-Dimensional Infrared Spectroscopy”, J. Phys. Chem. B 115, 13093-13100 (2011). [3] C. Costard, I. A. Heisler, T. Elsaesser, “Structural Dynamics of Hydrated Phospholipid Surfaces Probed by Ultrafast 2D Spectroscopy of Phosphate Vibrations”, J. Phys. Chem. Lett. 5, 506-511 (2014). [4] R. Costard, C. Greve, I. A. Heisler, T. Elsaesser, “Ultrafast Energy Redistribution in Local Hydration Shells of Phospholipids – a Two-Dimensional Infrared Study”, J. Phys. Chem. Lett. 3, 3646-3651 (2012).

Speaker: Prof. Thomas Elsaesser (Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin)

15:00 break

43 Modeling the Structure, Dynamics, and Vibrational Spectroscopy of Water and Ice

We have used the E3B water model, which includes three- body interactions, to simulate ice Ih as well as LDA and HDA, bulk liquid water, and the liquid/vapor interface. In addition we have studied the water hexamer, salt solutions, water confined in reverse micelles and lipid multibilayers, and water at lipid and surfactant monolayer interfaces. For all of these systems we have calculated various vibrational spectroscopic observables and compared with experiment. In this talk I will focus on a selection of these studies, emphasizing new insights that have emerged from this work.

Speaker: Prof. Jim Skinner (University of Wisconsin)

16:30 Travel to the City Hall

18:00 Reception at City Hall hosted by the City of Stockholm

Thursday 23 October

44 Roles of Local Structural Ordering in Thermodynamic Anomalies and Crystallization of Water

The anomalous thermodynamic and kinetic behaviour of water is known to play a fundamental role in many chemical, biological, geological and terrestrial processes. However, its origin is still much debated despite decades of intense research. An early insight, which dates back to Rontgen, is that the complexity of water may be modelled by a mixture of two structural motifs, but the idea has found limited support due to the lack of microscopic evidence. Unlike assuming the presence of two structural motifs, we proposed a two-order-parameter model of liquid [1,2], which focuses on the (cooperative) formation of locally favoured structures in a sea of random liquid structures. Here we provide a simple physical description of water anomaly from microscopic data obtained through computer simulations. We introduce a novel structural order parameter, which quantifies the degree of translational order of the second shell, and show that this parameter alone, which measures the amount of locally favored structures, accurately characterizes the state of water [3]. A two-state modeling of these microscopic structures [1,2] is used to describe the behavior of liquid water over a wide region of the phase diagram, correctly identifying the density and compressibility anomalies, and being compatible with the existence of a second critical point in the deeply supercooled region. Furthermore, we reveal that locally favored structures in water not only have translational order in the second shell, but also contain five-membered rings of hydrogen-bonded molecules. This suggests their mixed character: the former helps crystallization, whereas the latter causes frustration against crystallization [3]. We also show that this local structural ordering plays a key role in ice crystallization of a deeply supercooled water, through a novel metastable ice crystal phase, which we named Ice 0 [4]. We also discuss the glass-forming ability of water-type tetrahedral liquids, focusing on the friendliness of local structural orderings with a crystal structure to be nucleated. This work is performed in collaboration with John Russo and Flavio Romano. [1] H. Tanaka, Thermodynamic anomaly and polyamorphism of water, Europhy. Lett. 50, 340 (2000). [2] H. Tanaka, Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization, Eur. Phys. J. E 35, 113 (2012). [3] J. Russo and H. Tanaka, Understanding water's anomalies with locally favored structures, Nat. Commun. 5, 3556 (2014). [4] J. Russo, F. Romano, and H. Tanaka, New metastable form of ice and its role in the homogeneous crystallization of water, Nature Mater. 13, 733 (2014).

Speaker: Prof. Hajime Tanaka (University of Tokyo)

10:00 break

45 Widom Lines and Dynamic Crossovers in Water

In this talk I shall summarize recent results from computer simulations that address two important issues: how can the Widom line of water both in the supercritical and in the supercooled states help to characterize its properties and how can aqueous solutions and confinement help to shed light on water properties in the supercooled region. The Widom line is the line of convergence of the maxima of the thermodynamic response functions upon approaching a critical point. The characterization of this line is very important in water both in the supercooled and in the supercritical state and it can be found upon approaching respectively the liquid-liquid and the liquid gas critical points. I will analyze the thermodynamic properties of bulk water in the supercritical region by comparing experimental results and computer simulation results along the isobars. The lines connecting the maxima of the thermodynamic response functions converge upon approaching the critical point to a single Widom line separating a liquid-like region from a gas-like region. This Widom line of supercritical water is connected to the crossover from a liquid-like to a gas-like behaviour of the transport coefficients [1]. In the supercooled state the experimental determination of the liquid-liquid critical point can be eased in aqueous solutions depending on the solute, as computer simulations show that its position is shifted in the thermodynamic planes with respect to the bulk [2]. I will characterize the Widom line in hydrophilic [3], amphiphilic [4] and hydrophobic [5] aqueous solutions. I will also show that the Widom line emanating from the LLCP can be connected to dynamic crossovers in solutions. Dynamics crossovers are associated to the crossing of the Widom line both for the Jagla liquid with hard spheres [5] and for the aqueous solutions of NaCl [6,7] and the results found in solutions are comparable to those found in the bulk [8]. In correspondence with the dynamic crossovers I will show that the two-body entropy [9] also shows a change of behaviour and the relation that connects the two body entropy and the relaxation time in the region where Mode Coupling Theory is valid does not hold any more. I will finally briefly discuss the connection between a dynamic crossover and the Widom line also in confinement [10,11]. [1] P. Gallo, D. Corradini and M. Rovere, submitted (2014). [2] D. Corradini, M. Rovere and P. Gallo, J. Chem. Phys. 132, 134508 (2010). [3] D. Corradini and P. Gallo, J. Phys. Chem. B. 115, 14161 (2011). [4] D. Corradini, Z. Su, H.E. Stanley and P. Gallo, J. Chem. Phys. 187, 184503 (2012). [5] D. Corradini, P. Gallo, S.V. Buldyrev and H.E. Stanley, Phys. Rev. E 85, 051503 (2012). [6] P. Gallo, D. Corradini and M. Rovere, Mol. Phys, 109, 2069 (2011). [7] P. Gallo, D. Corradini and M. Rovere, J. Chem. Phys. 139, 204503 (2013). [8] P. Gallo and M. Rovere, J. Chem. Phys., 137 , 164503 (2012). [9] P. Gallo and M. Rovere, submitted (2014). [10] P. Gallo, M. Rovere and S.-H. Chen, J. Phys.: Condens. Matter 24 064109 (2012). [11] P. Gallo, M. Rovere and S.-H. Chen J. Phys. Chem. Lett. 1, 729 (2010).

Speaker: Prof. Paola Gallo (Università di Roma Tre)

46 Water at Interfaces. Is That a Good Model for Bulk Water?

Laponite is a synthetic disc-shaped crystalline clay belonging to the family of swelling smectites. To date it is the most widely studied synthetic clay on account of its special chemical and physical properties, making it promising both as ''smart'' material suitable for several industrial and biomedical applications and as model system for fundamental studies on phase transitions and water molecules-charged surfaces interaction [1]. We have performed dielectric relaxation experiments on laponite powder with about 4 water layers of hydration around each laponite disc (Fig. 1A), over a broad interval of frequencies, ranging from 10-3 to 107 Hz, and over the temperature range between 150 and 300 K. The aim of this work is to study the orientational dynamics of water molecules close to the laponite surface. In particular, we examined the temperature dependence of the relaxation process assigned to the collective dynamics of the hydrogen bond (HB) network. Preliminary results indicate the presence of two dynamical crossovers of this collective relaxation time (Fig. 1B): the first one (at about 260 K) identifies two different Vogel-Fulcher- Tamman (VFT) regimes, while at about 170 K a second crossover identifies a dynamical transition from a VFT to a Arrhenius temperature dependence of the relaxation time. This situation is quite similar to what previously observed for water molecules in the first hydration shell of a globular protein [2]. In this latter case, a coarse-grained model of water molecules helped us to attribute the observed crossovers to the thermodynamics of the HB network, with two specific heat maxima. The high temperature maximum is caused by fluctuations in the HB formation, while the low temperature maximum is due to the cooperative reordering of the HB network. [1] Ruzicka B. et al., Soft Matter 7, 1268-1286 (2011). [2] Mazza et al., PNAS, 108, 19873 (2011).

Speaker: Prof. Fabio Bruni (Università di Roma Tre)

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12:30 Lunch

13:30 Travel to the Museum

15:00 Nobel Museum

Friday 24 October

47 GW/Bethe-Salpeter Equation Calculations of the X-ray Absorption Spectra of Water

We calculate x-ray absorption spectra (XAS) of water within a GW/Bethe-Salpeter Equation (BSE) approach using the OCEAN code [1-3]. This hybrid code combines ab initio plane- wave, pseudopotential electronic structure, PAW transition- matrix elements, GW self-energy corrections, and the NIST BSE solver [1]. Due to the computational demands, our previous XAS calculations [2] were limited to 17 molecule super cells. This limitation causes unphysical, size dependent effects in the calculated spectra. In order to treat much larger systems several improvements were necessary [3]: 1) we extended the OCEAN interface to support well-parallelized codes such as QuantumESPRESSO; 2) we implemented an efficient interpolation scheme due to Shirley. We have applied this large-scale GW/BSE approach to 64 molecule unit cell structures of water obtained from classical DFT/MD and PIMD simulations [4]. In comparison with previous work [5], we obtain improved spectra that agree semi-quantitatively with experimental features. The agreement suggests that the 64 molecule unit cell PIMD structures, which are similar to the traditional distorted tetrahedral view, are consistent with experimental observations. [1] J. Vinson et al., PRB 83, 115106 (2011); J. Vinson and J.J. Rehr, PRB 86, 195135 (2012). [2] J. Vinson et al., PRB 85, 045101 (2012). [3] K. Gilmore, J. Vinson, E.L. Shirley, D. Prendergast, J. J. Kas and J. J. Rehr, UW Preprint 2014. [4] J.A. Morrone and R. Car, PRL 101, 017801 (2008). [5] L. Kong et al., PRB 86, 134203 (2012).

Speaker: Prof. John Rehr (University of Washington)

10:00 break

48 A Combined Approach of X-ray, Vibrational and Electronic Spectroscopy of Water

X-ray and neutron diffraction techniques have long been used as a direct probe of the hydrogen bond network of liquid water, while in this decade X-ray spectroscopic techniques have been widely used with the development of high brilliance synchrotron radiation source. X-ray absorption (XAS) and emission (XES) spectra of liquid water are one of the recently debated approaches to determine the local hydrogen bond network of liquid water through observation of its local valence electronic structure [1]. Here we review our X-ray emission technique and spectroscopic results including temperature [2], isotope [3] and polarization [4] dependence by referring those debates. In addition, recent high resolution O 1s resonant inelastic X-ray scattering (RIXS) spectra add information about vibrational energy in the OH-stretching mode. Figure 1 shows a comparison of the energy separation in the RIXS spectrum at XAS pre-edge excitation of liquid H2O water with the OH stretching mode by Raman spectroscopy [5]. The RIXS spectrum is blue shifted because water molecules with a highly weakened or broken donating hydrogen bond are selected by the pre-edge excitation. We will also show evidence of this selectivity by excitation energy dependence of the RIXS vibrational structure, which strongly supports the interpretation of our O 1s XAS/XES results in terms of a mixture (micro-heterogeneity) model, where the network is considered as a mixture of various hydrogen bond configurations. The ‘vibrational RIXS’ technique bridges hydrogen bond configuration and the electronic structure of water, which can be applied to a wide range of solutions in the near future. [1] A. Nilsson and L. G. M. Pettersson, Chem. Phys. 389, 1 (2011). [2] T. Tokushima, Y. Harada, O. Takahashi, Y. Senba, H. Ohashi, L. G. M. Pettersson, A. Nilsson, and S. Shin, Chem. Phys. Lett. 460, 387 (2008). [3] T. Tokushima, Y. Harada, Y. Horikawa, O. Takahashi, Y. Senba, H. Ohashi, L. G. M. Pettersson, A. Nilsson, and S. Shin, J. Electron Spectrosc. Relat. Phenom. 177, 192 (2010). [4] T. Tokushima, Y. Horikawa, H. Arai, Y. Harada, O. Takahashi, L. G. M. Pettersson, A. Nilsson, S. Shin, J. Chem. Phys. 136, 044517 (2012). [5] Y. Harada, T. Tokushima, Y. Horikawa, O. Takahashi, H. Niwa, M. Kobayashi, M. Oshima, Y. Senba, H. Ohashi, K. Wikfeldt, A. Nilsson, L. G. M. Pettersson, S. Shin, Phys. Rev. Lett. 111, 193001 (2013).

Speaker: Prof. Yoshihisa Harada (University of Tokyo)

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49 Ab-Initio Liquid Water

Ab-initio molecular dynamics simulations of condensed water phases depend critically on the adopted approximations of electronic density functional theory. Accurate functionals include van der Waals interactions and have reduced self- interaction errors. In addition, quantum mechanical delocalization of the nuclei cannot be ignored when comparing ab-initio simulations and experiment. In this talk, I will discuss the influence of all these effects on the hydrogen bond network of clean water and the solvation structures of the water ions and the hydroxyl radical. Finally, I will comment on the nature of disorder in water and amorphous ice structures, and how this reflects on the x-ray absorption spectra.

Speaker: Prof. Roberto Car (Princeton University)

12:30 Lunch

50 Water and Protein Activity (Nuclear Magnetic Resonance and Infrared Spectroscopy Studies from the Protein Dynamical Crossover to the Irreversible Unfolding)

The effect of water on lysozyme is studied in a very large temperature range from 180 to 370 K. By using in a comparative way the Nuclear Magnetic Resonance and the FTIR spectroscopy (the vibrational modes) we explore this protein system at different hydration level h (h=0.3, 0.37, 0.42). The hydration level h=0.3 is equivalent to a single monolayer of water around the globular protein. Our interest is focused to study the water role in the protein dynamical transition (glass transition or the transition from an harmonic solid like behavior to an anharmonic and liquid like motion) and the irreversible unfolding. We demonstrate also by considering previous neutron scattering experiments that the protein dynamical transition belongs to the universal class of dynamical crossover characterizing supercooled liquids and materials. By means of a detailed study of the bending vibrational mode of water and of the amide’s peptide (amide I, II and III) we were able to follow the dynamics of the complex hydrogen bond (HB) network formed between water and hydrophilic moieties of the protein. In particular the amide II Infrared region (1450 – 1580 cm-1) contains structural information about the protein conformation reflected in the bending mode of NH groups and in the stretching mode of CN groups. Both these groups are involved in the formation of hydrogen bonds, the NH in a direct way whereas the CN indirectly throughout the carbonyl oxygen, determining the water accessible regions. More precisely these bonds have different character, whereas one is proton donor the other is proton acceptor by linking hydrophilic groups of the same and/or different peptides. The thermal evolution of the spectral features regarding these two contributions allows identifying that the dynamical crossover observed for water coincides with that of the protein dynamical transition. We stress that we are able to demonstrate at a molecular level the interaction of water with the protein peptides and how via the HB it drives the protein activity. Furthermore, the combination of FTIR, Neutron Scattering and NMR data (under a novel interpretation) allows us to clarify some of the underlying mechanisms that govern the reversibility of the folding-unfolding and irreversible denaturation processes of the protein. In particular, new NMR observations at the temperature above and below the protein irreversible unfolding (TD) show that folding-unfolding process takes place as a function of the temperature; we observe that T acts as a control parameter of the measured nuclear magnetization M(T). Whereas far from this singular temperature, in the protein native state, the M(T) behavior is Arrhenius, approaching TD (in a large T-interval) the system changes dramatically it energetic configurations by means a power law behavior. Hence, by following the thermal behavior of different protein-peptide metabolites we are able to explore the funneled energy landscape. On these bases, by taking advantage of the polymer physics we propose this complex process (protein folding/unfolding) as a sort of sol- gel transition driven by water as the cross-linker between different protein peptides, an with TD as the percolation threshold temperature.

Speaker: Prof. Francesco Mallamace (Universita di Messina and CNR-IPCF, Massachusetts Institute of Technology, Boston University)

51 Effects of Hydrophobic/Hydrophilic Surfaces on the Phase Behaviors of Water

The phase behavior of water is important for the understanding of many physical, biological and chemical processes, especially in nano-confinement. In this presentation, I will talk about some of our results on the phase behavior of confined water. Specifically, I will discuss how the nanoscopic surfaces, such as hydrophobic confinement, hydrophilic confinement, and janus confinement, affect the phase behavior of water.

Speaker: Prof. Limei Xu (Peking University)

15:30 break

52 My Personal Thoughts About the Relaxation Behaviour of Supercooled Water

In this presentation I will give my personal thoughts about the calorimetric and relaxation behavior of supercooled bulk water, based mainly on studies of supercooled water and aqueous solutions in confinements. Such studies show that confined water lacks a clear calorimetric glass transition and associated viscosity related structural relaxation process. This finding is in contrast to most other liquids and indicates that the dynamics associated with the glass transition of bulk water involves an exceptionally large volume of cooperatively rearranging regions at temperatures close to the glass transition temperature, Tg, due to the completion of an ice- like tetrahedral network structure close to Tg. In confinements, where ice formation can be prevented, no similar structural relaxation process can occur due to the geometrical restrictions and no Tg is consequently observed. For confined water-glycerol solutions the glass transition and its associated structural relaxation can be observed up to a water concentration of about 90 wt%. At this high water concentration Tg increases (and the structural relaxation slows down) with increasing water content, indicating that the added water has an anti-plasticizing effect on the glycerol molecules at such a high water concentration, due to the rigidity of a nearly tetrahedral hydrogen bonded network structure of water at low temperatures. The results further predict that Tg of bulk water should be located at an unexpectedly high temperature, i.e. at least above 190 K. This further implies that the results from these confinement studies seem to be in conflict with previous results for glassy bulk water. Reasons for this apparent conflict and possible misinterpretations are discussed. Finally, I give my personal thoughts about the possible liquid-liquid transition of supercooled water.

Speaker: Prof. Jan Swenson (Chalmers University of Technology)

Monday 27 October

53 Welcome

54 Jan Erik Rubensson

10:00 Discussion

10:15 break

55 Marie-Claire Bellissent-Funel

11:30 Discussion

11:45 Lunch

56 Foivos Perakis / Yuki Nagata

13:45 Discussion

57 Jan Swenson

14:45 Discussion

15:00 break

15:30 Working Group Discussions

Tuesday 28 October

58 John Rehr

59 Lawrie Skinner

60 Luigi DeMarco

10:45 break

61 Francesco Mallamace

62 Limei Xu

63 Andrey Shalit

13:00 Lunch

14:00 Working Group Discussions

15:30 break

16:00 Working Group Discussions

16:30 Summary of Discussions

Wednesday 29 October

64 Gerhard Grubel

65 Yoshi Harada

66 Lothar Weinhardt

10:45 break

67 Sylvia Cerveny

11:50 Writing in Working Groups

13:00 Lunch

14:00 Excursion to the Wasa Museum

Thursday 30 October

68 Alessandro Paciaroni

69 Zachary Kann

70 Michael Vogel

10:45 break

71 Roberto Car

72 Nicholas Besley

73 Nobuhiro Kosigu

13:00 Lunch

14:00 Writing in Working Groups

15:30 break

16:00 Writing in Working Groups

Friday 31 October

74 Katrin Amann-Winkel

75 Livia Bove

10:10 break

10:45 Writing in Working Groups

13:00 Lunch

14:00 Discussion and Summary of the Week

Monday 3 November

76 Welcome

77 Ali Hassanali

10:00 Discussion

10:15 break

78 Angel Garcia

11:30 Discussion

11:45 Lunch

79 Hendrik Bluhm

13:45 Discussion

80 Nico van der Vegt

14:45 Discussion

15:00 break

15:30 Working Group Discussions

Tuesday 4 November

81 Noam Agmon

82 Fabio Sterpone

83 Andrew Hodgson

10:45 break

84 Mikael Lund

85 Peter Pohl

86 Philipp Pedevilla

13:00 Lunch

14:00 Working Group Discussions

15:30 break

16:00 Working Group Discussions

16:30 Summary of Discussions

Wednesday 5 November

87 Eric Tyrode

88 Martin Thaemer

89 Marie-Claire Bellissent-Funel

10:45 break

90 Sylvie Roke

11:50 Writing in Working Groups

13:00 Lunch

14:00 Excursion to the Nobel Museum

Thursday 6 November

91 Huib Bakker

92 David van der Spoel

93 Olle Björneholm

10:45 break

94 Kramer Campen

95 Junrong Zheng

12:25 Lunch

14:00 Writing in Working Groups

15:30 break

16:00 Writing in Working Groups

16:30 Summary of Discussions and Writing

Friday 7 November

96 Kristoffer Haldrup

97 Martin Hansen

10:10 break

10:45 Writing in Working Groups

13:00 Lunch

14:00 Discussion and Summary of the Week