Factors affecting molecular dynamics simulated vitreous silica structures

To obtain accurate results in molecular dynamic (MD) simulations of glasses , it is essential to chose proper force fields (FF), proper length of the s imulation cell, and proper cooling cycle to generate 300 K structures from liquid. Herein we establish guidelines for these choices. We find that the MS-Q force field (FF) and the Molecular Simulations Incorporated (MSI) glas s FF both lead to agreement with the radial distribution function (RDF) fro m small angle neutron scattering (SANS) experiments. We find that the simul ation cell should contain about 3000 atoms to obtain run to run density var iation less than 1% and consistency in the first two RDF peaks of 0.001 nm, A cell of 648 atoms gives run to run density variation of up to 5% and con sistency in the first three RDF peaks of 0.001 nm, We find that a good comp romise between accuracy and reproducibility of results and simulation time is to start with NVT dynamics at 8000 K followed by cooling to room tempera ture at a rate of 100 K/2 ps, (C) 1999 Published by Elsevier Science B.V. A ll rights reserved.