Diffusion of sodium ions in borosilicate glasses by molecular dynamics method

Abstract

Molecular dynamics simulations of borosilicate glasses with different sodium oxide content has been carried out. The generated structure indicates that the major number of oxygen atoms introduced as Na₂O consumes in the borate network to convert the BO₃ triangles to BO₄ tetrahedra. The formation of nonbridging oxygen ions in the silica site occurs during the formation of BO₄ tetrahedra with low rate. At higher concentrations of Na₂O, the NBO's increases abruptly. The self diffusion of sodium ions depends essentially on the temperature, composition (number of Na⁺ ions) and the rate of cooling. The phase separation mechanism in borosilicate glasses can be detected by MD simulation since the environment of the B−O, Si−O and B−O−Si can be easily reached.