The Interface Response Function and Melting Point of the Prism Interface of Hexagonal Ice using a Fluctuating Charge Model (TIP4P-FQ)

Abstract

Molecular Dynamics simulations have been used to follow the rate of growth and recession of the prismatic surface of a hexagonal ice-water interface. The fluctuating charge, four-site transferable intermolecular potential model, TIP4P-FQ, was used at temperatures between 265 K and 310 K in a series of isobaric isothermal (NPT) Molecular Dynamics simulations. Using appropriate order parameters, an interface response function that captures the speed of the moving interface as a function of temperature was constructed that covers the melting and growth of hexagonal ice. From the interface response function (Tv=0), the melting temperature was found to be within 8 K of 303 K and the maximum crystallization velocity was estimated to be ~1 m/s at 260 K (14% undercooling; in line with the kinetics of other systems such as Si). Changing the Lennard-Jones sigma parameter from 3.159 angstroms to 3.173 angstroms, in line with a previous parameterization by Rick, confirms results from Gibbs-Duhem integration that predicted a reduction in the melting temperature to 276 K. While this value corresponds well with experiments, given the relative simplicity of the model, it comes at the expense of accurately predicting the properties of liquid water. Crystallization from the prism interface involves at least two layers, as determined by density and dipole analysis and is in line with results found from previous TIP6P results.