The role of Ti in mitigating thermal expansion of silica from molecular dynamics simulations

Molecular dynamics simulations are performed to investigate the structural response of titania silicate glass to temperature. The coefficient of thermal expansion is computed for two titania silicate glasses with 0 and 10 mol% titania content, the structures of which are presented in terms of radial and angular distributions. Revealed by the different changing rates of intertetrahedra bond angles and bond lengths with respect to the Ti and Si atoms, the glass structures tend to exhibit a nonvectorized expansion process at elevated temperatures, leading to inconsistent expansion rates of the structures in different scales. While the average length of TiO and Si-O bonds both increases with temperature, the decrease in the coefficient of thermal expansion by the addition of Ti atoms is associated with the different expansion rate of tetrahedra. Arising from the gradual decrease in atomic overlapping, decrease in free volume inside the glass with temperature is also identified.