Local Dynamics and Viscosity in Liquid: Application for Water and Colloid

by Takeshi Egami (Oak Ridge National Laboratory and University of Tennessee, Joint Institute for Neutron Sciences, Department of Materials Science and Engineering, Department of Physics and Astronomy)

Monday 30 May 2016, 10:00 → 11:00 Europe/Stockholm

FD41

Liquid, water in particular, is so vitally important to our life. Yet our understanding of the physics of liquid is much poorer than that of solid. This is because most of the theoretical tools of solid state physics assumes periodicity, whereas liquid is aperiodic and even dynamic. For instance in liquid phonons are overdamped and essentially dead, but we don’t know what the primary modes of excitation in liquid are. Viscosity is one of the most fundamental properties of liquid, yet its atomistic origin is unclear. Based upon computer simulations and inelastic scattering experiments we propose a novel view of liquid dynamics and the origin of viscosity, based on the dynamics of local topology of atomic connectivity network. Through simulation we discovered that the local topological excitations in the atomic connectivity network are the elementary excitations in the liquid and determine viscosity [1]. They also govern the flow of the liquid under shear through local elasticity [2]. We recently confirmed these findings by inelastic x-ray scattering from water and elastic neutron scattering from colloids under shear. These findings hopefully would form the basis for the new topological view of liquids and glasses. [1] T. Iwashita, D. M. Nicholson and T. Egami, Phys. Rev. Lett., 110, 205504 (2013). [2] T. Iwashita and T. Egami, Phys. Rev. Lett., 108, 196001 (2012).