Molecular dynamics computer simulation of amorphous silica under high pressure

Abstract

The structural and dynamic properties of silica melts under high pressure are studied usingmolecular dynamics (MD) computer simulation. The interactions between theions are modelled by a pairwise-additive potential, the so-called CHIK potential,that has been recently proposed by Carré et al 2008 Europhys. Lett. 82 17001. Theexperimental equation of state is well reproduced by the CHIK model. With increasingpressure (density), the structure changes from a tetrahedral network to a networkcontaining a high number of five- and six-fold Si–O coordinations. In the partialstatic structure factors, this change of the structure with increasing density isreflected by a shift of the first sharp diffraction peak towards higher wavenumbersq, eventually merging with the main peak at densities around4.2 g cm−3. The self-diffusion constants as a function of pressure show the experimentally knownmaximum, occurring around a pressure of about 20 GPa.