EVOLUTION OF STRUCTURE OF LIQUID AND AMORPHOUS Al2O3·2SiO2 NANOPARTICLES UPON COOLING FROM THE MELTS

Abstract

Structural properties of liquid and amorphous Al 2 O 3·2 SiO 2 nanoparticles have been investigated by molecular dynamics (MD) method. The simulations were done in a spherical model with different sizes of 2 nm, 3 nm and 4 nm under nonperiodic boundary conditions. We use the Born–Mayer type interatomic potentials. We determined the changes in mean interatomic distances, coordination number distributions, partial radial distribution functions (PRDFs) and bond-angle distributions of Al 2 O 3·2 SiO 2 nanoparticles upon cooling towards glassy state. Calculations show that liquid and amorphous Al 2 O 3·2 SiO 2 nanoparticles have a slightly distorted tetrahedral network structure with the mean coordination number Z Al - O ≈ 4.0 and Z Si - O ≈ 4.0, which is contrary to that of the liquid and amorphous bulk. Temperature dependence of structural defects in nanoparticles was found and discussed. In addition, we found size effects on glass transition temperature of Al 2 O 3·2 SiO 2 nanoparticles in that it decreases with decreasing size.