Investigating the crystallization behavior of TiO2 during annealing: Molecular dynamics simulations

Abstract

TiO2 is a dielectric material with excellent photocatalytic and photochemical properties. The conversion of TiO2 from an amorphous to crystalline phase significantly improves the photocatalytic activity of TiO2. However, the crystallization behavior of TiO2 during annealing has been little studied in the field of molecular dynamics. In this paper, the crystallization behavior of TiO2 during annealing under different conditions was analyzed using molecular dynamics simulation. To investigate the phase transition process of TiO2, the melting point temperature of the system was calculated by mean square displacement at about 2400 K. The effect of size on structural stability was explored. The radial distribution function and x-ray diffraction curves revealed that the anatase phase appeared over 800 K. Moreover, with the increase in annealing temperature, the anatase content in TiO2 first increased and then decreased, and the rutile phase gradually increased. At a specific temperature, a structure is formed where rutile and anatase coexist. Anatase atoms compete with rutile atoms, and by increasing the temperature, anatase is converted to rutile. The amorphous structure is reduced at high temperatures, improving the crystalline quality. The crystallization behavior of the amorphous structure can improve the photocatalytic efficiency of TiO2. TiO2 nanometers have good prospect for application. Therefore, studying the crystallization behavior of TiO2 is essential.