COOLING RATE EFFECTS ON DYNAMICS IN SUPERCOOLED Al2O3

Abstract

The cooling rate effects in supercooled Al 2 O 3 have been investigated by Molecular Dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with Born–Mayer type pair potentials. The temperature of the system was decreased linearly in time as T(t)=T0–γt, where γ is the cooling rate. The cooling rate dependence of density, thermal expansion coefficient and enthalpy of the system was found. Structure of amorphous Al 2 O 3 model at the temperature of 0 K was in good agreement with Lamparter's experimental data. The cooling rate dependence of the dynamical heterogeneities in supercooled states has been studied through the comparison of the partial radial distribution functions (PRDFs) for the 10% most mobile or immobile particles with the corresponding mean PRDFs in the models. Also, cooling rate effects on the cluster size distributions of the most mobile or immobile particles have been obtained. Calculations show that the cooling rate effects on the dynamical heterogeneities are pronounced. Finally, the evolution of structural defects and cluster size distributions of the most mobile or immobile particles in the system upon cooling has been studied and presented.