Anisotropy in growth kinetics at interfaces between proton-disordered hexagonal ice and water: A molecular dynamics study using the six-site model of H2O

Abstract

Molecular dynamics simulations of interfaces between proton-disordered hexagonal ice and water are carried out at a temperature near the melting point and a pressure of 1 atm using the six-site model of H2O, which was recently proposed for simulation studies of ice and water near the melting point. The simulations are performed for the interfaces of basal, prismatic and {112¯0} planes of ice. The growth process of ice is clearly observed on all planes. It is observed, during growth on the {112¯0} plane, the {112¯0} plane disappears and prismatic planes appear instead. The result suggests that the growth velocity at the interface is larger for the {112¯0} plane than for the prismatic plane. The structure of each interface and growth kinetics at each interface are analyzed on a molecular scale. Simulations show the interfaces of the prismatic and the {112¯0} planes have a geometrically rough structure, whereas the interface of the basal plane has a molecularly flat structure. The simulations also show, that on all planes, growth occurs by reorganization of the hydrogen-bonded network in water near the interface. The reorganization occurs three-dimensionally on the prismatic and the {112¯0} planes, whereas two-dimensionally on the basal plane. The anisotropy in the growth velocity, which is obtained in the present study, is qualitatively consistent with previous experiments. It is shown that the present results on the anisotropy in the interface structure and growth kinetics qualitatively explain the macroscopic shape of ice growing from water in a real system.