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

We present a classical interatomic force field, silica-DDEC,todescribe the interactions of amorphous and crystalline silica surfaces,parametrized using density functional theory-based charges. Chargeschemes for silica surfaces were developed using the density-derivedelectrostatic and chemical (DDEC) method, which reproduces atomiccharges of the periodic models as well as the electrostatic potentialaway from the atom sites. Lennard-Jones parameters were determinedby requiring the correct description of (i) the amorphous silica density,coordination defects, and local coordination geometry, relative toexperimental measurements, and (ii) water-silica interatomic distancescompared with ab initio results. Deprotonated surface silanol sitesare also described within the model based on DDEC charges. The resultis a general electronic structure-derived model for describing fullyflexible amorphous and crystalline silica surfaces and interactionsof liquids with silica surfaces of varying structure and protonationstate.