The glass transition and thermodynamics of liquid and amorphousTiO2 nanoparticles

Abstract

The glass transition and thermodynamics of spherical liquidTiO2 nanoparticles, with different sizes ranging from 2 to 5 nm, have been studied in a modelunder non-periodic boundary conditions. We use the pairwise interatomic potentialsproposed by Matsui and Akaogi. Models have been obtained by cooling from the melt viamolecular dynamics (MD) simulation. The structural properties of liquid nanoparticles at3500 K have been analyzed in detail through the partial radial distribution functions(PRDFs), coordination number distributions, bond-angle distributions and interatomicdistances. Moreover, we also show the radial density profile in nanoparticles. Calculationsshow that size effects on the structure of a model are significant and that liquidTiO2 nanoparticles have a distorted pentahedral network structure with the mean coordination numbersZTi–O≈5.0 andZO–Ti≈2.5, whileamorphous TiO2 nanoparticles have an octahedral network structure. The temperature dependence of thesurface structure and surface energy of the nanoparticles has been obtained and ispresented. In addition, the size dependence of the glass transition temperature and thetemperature dependence of the diffusion constant of atomic species have been found andare discussed.