Molecular Physics seminar

Molecule substrate registry on h-BN supported by Rh(111) and other metallic surfaces

by Marcella Iannuzzi (Physical Chemistry Institute, University of Zurich)

FA31 ()


The investigation of properties and processes at complex interfaces between metallic substrates and adsorbed molecular systems requires the design of reliable models and efficient computational tools.[1] Working in close collaboration with experimentalists, we are constantly challenged to reproduce and/or interpret the observed be- haviours. The final goal is to acquire in depth knowledge of the studied systems such to lead to the development of new materials with tailored properties. Modern nano-templates based on hexagonal boron nitride or graphene grown on transition metals[2–5] show potential for future applications, due to their outstanding mechanical, thermal and electronic properties. The mismatch between the lattice constant of the sp2 overlayer and the substrate produces modulated structures, which act as nano-templates for self-assembly, electron confinement, or intercalation. We apply scanning tunneling microscopy (STM) and density functional theory to investigate the adsorption of molecules and the formation and dynamics of defects.[6] In particular, the site-selectivity of h-BN/Rh(111) (nanomesh) for the adsorption of hexaiodo-cyclo-hexaphenylene (I6 -CHP)[7] and H2 -phthalocyanine[8] is dis- cussed. In both cases we observe the preferential absorption within the pore of the nanomesh and the preferential orientation with respect to the substrate. Advanced sampling techniques and tuned analysis tools lead to a better understanding of the interaction between adsorbate and substrate, which could be exploited in the development of new structure and process, as the production of graphene derivatives on metal supported insulators. Self assembled monolayers of single molecule magnet (SMM) (as organic free radicals with specific magnetic properties or functionalized clusters of transition metal ions) represent another interesting class of interfaces, to be used as high density memory storage systems or spintronic devices. The challenge in this case is to shed some light on the magnetic properties of the molecules once grafted on surfaces and to explore the complexity of the structural rearrangement of the functionalized systems and how this affects the magnetic properties.[9] We also propose a QM/MM approach to describe the interaction between physisorbed molecules and metallic substrates, where image charges within the substrate are used to model the response of the metallic electronic structure to the electrostatic potential generated by the adsorbed molecule.[10] The method is employed, for instance, to simulate liquid/metal interfaces, where the liquid (water) is treated QM and the metal is described by an empirical force field. The image charge scheme accounts for the polarization effects, thus reducing significantly the computational costs with respect to a full QM calculation.[11] [1] J. Hutter, M. Iannuzzi, F. Schiffmann, and J. VandeVondele, WIREs Comput Mol Sci 4, 15 (2013). [2] J. G. Diaz, Y. Ding, R. Koitz, A. P. Seitsonen, M. Iannuzzi, and J. Hutter, Theor Chem Acc 132 (2013). [3] H. Ma, Y. Ding, M. Iannuzzi, T. Brugger, S. Berner, J. Hutter, J. Osterwalder, and T. Greber, Langmuir 28, 15246 (2012). [4] S. Joshi, D. Ecija, R. Koitz, M. Iannuzzi, A. P. Seitsonen, J. Hutter, H. Sachdev, S. Vijayaraghavan, F. Bischoff, K. Seufert, et al., Nano Lett 12, 5821 (2012). [5] H. Cun, M. Iannuzzi, A. Hemmi, S. Roth, J. Osterwalder, and T. Greber, Nano Lett 13, 2098 (2013). [6] H. Cun, M. Iannuzzi, A. Hemmi, S. Roth, J. Osterwalder, and T. Greber, ACS Nano (2013). [7] T. Dienel, J. Gomez-Diaz, A. Seitsonen, R. Widmer, M. Iannuzzi, K. Radican, H. Sachdev, K. Müllen, J. Hutter, and O. Gröning, submitted (2014). [8] M. Iannuzzi, F. Tran, T. Dienel, R. Widmer, Y. Ding, J. Hutter, and O. Gröning, in preparation (2014). [9] F. Totti, G. Rajaraman, M. Iannuzzi, and R. Sessoli, Journal of Physical Chemistry C 117, 7186 (2013). [10] J. I. Siepmann and M. Sprik, J Chem Phys 102, 511 (1995). [11] D. Golze, M. Iannuzzi, D. Passerone, and J. Hutter, J. Chem. Theo. Comp. 9, 5086 (2013).