Ab Initio-Derived Force Field for Amorphous Silica Interfaces for Use in Molecular Dynamics Simulations

We present a classical interatomic force field, silica-DDEC,
to
describe the interactions of amorphous and crystalline silica surfaces,
parametrized using density functional theory-based charges. Charge
schemes for silica surfaces were developed using the density-derived
electrostatic and chemical (DDEC) method, which reproduces atomic
charges of the periodic models as well as the electrostatic potential
away from the atom sites. Lennard–Jones parameters were determined
by requiring the correct description of (i) the amorphous silica density,
coordination defects, and local coordination geometry, relative to
experimental measurements, and (ii) water-silica interatomic distances
compared with ab initio results. Deprotonated surface silanol sites
are also described within the model based on DDEC charges. The result
is a general electronic structure-derived model for describing fully
flexible amorphous and crystalline silica surfaces and interactions
of liquids with silica surfaces of varying structure and protonation
state.