Structure and diffusion simulation of liquid Al2O3

Abstract

Structure and diffusion of liquid Al2O3 have been investigated by molecular dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with the BKS pair potentials. Structure of liquid models agrees reasonably with experiment. The microstructure of systems has been analyzed through partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Temperature dependence of these distributions was obtained. Calculations show that in the liquid Al2O3 model with real density at 2.80g/cm3 there is a short-range order dominated by distorted AlO4 tetrahedron, in agreement with Landron's experiment. Self-diffusion constants have been calculated. The temperature dependence of diffusion constants D in liquid Al2O3 shows an Arrhenius law with activation energy which is close to experimental one for liquid SiO2 and close to the calculated data for diffusion in liquid aluminum silicate. With increasing temperature we find that this dependence shows a crossover to one which can be described well by a power law, D∝(T-Tc)γ. The critical temperature Tc is about 3500K and the exponent γ is close to 0.50. We also present the effects of MD run time on the structure of models. The phase transition temperature Tg for the Al2O3 system is anywhere around 2100K.