Atomic diffusion in covalent liquids under pressure fromab initiomolecular dynamics

Abstract

Abstract. The microscopic mechanisms of atomic diffusion in liquid GeO 2 and SrGeO 3 are investigated by ab initio molecular-dynamics simulations. We clarify the differences of diffusion mechanism between liquid GeO 2 and SrGeO 3 . In both liquids, non-bridging oxygen double bonded to only one germanate plays a key role in the atomic diffusion mechanism. It is found that, in liquid SrGeO 3 which has non-bridging oxygen in the equilibrium state at ambient pressure, atomic diffusion is possible without generating overcoordinated atoms at ambient pressure, while the over coordinated atoms are always needed for the formation of non-bridging oxygens in liquid GeO 2 . When the pressure increases, only liquid GeO 2 has a diffusion maximum, which is given by, the atomic diffusion with concerted reaction gives the diffusion maximum.