Combiningab initio techniques with analytical potential functions for structure predictions of large systems: Method and application to crystalline silica polymorphs

Abstract

A computational scheme is presented which combines quantum mechanical ab initio techniques with methods using analytical potential functions. The scheme is designed for use in structure optimizations and is also applicable to molecular dynamics simulations. The implementation covers both molecular and periodic systems. The problem of the link atoms is solved by a subtraction scheme which is easily implemented for any combination of methods. As a first application dense and microporous silica polymorphs are studied. The Hartree-Fock method is combined with both a force field and an ion pair shell model potential. Comparison is made with lattice energy minimizations which use the force field or the shell model potential alone as well as with free cluster optimizations and optimizations in which the outer part of the cluster is kept fixed. © 1997 by John Wiley & Sons, Inc.