COMPUTER SIMULATION OF LOCAL STRUCTURE AND DIFFUSION MECHANISM THROUGH VORONOI POLYHEDRONS IN SODIUM SILICATE GLASS

DOI: 10.18173/2354-1059.2021-0044

Tóm tắt

The Na2O.SiO2 glass has been studied at different temperatures from 300 K to 1173 K by using molecular dynamics simulations. The Voronoi Si and O polyhedrons are analyzed to evaluate the displacement of sodium between these polyhedrons. The results show that more than 90% of the total number of Na is located in NBF polyhedrons that contain non-bridging (NBO) and free oxygen (FO) polyhedrons. The site energy for Na atoms located in NBF is smaller than one in BO polyhedron. The diffusion process of Na atoms is occurred in two ways: the first one is the alone jumping of Na in BO polyhedrons and the second one is the mixed alone jumping of Na and the cooperative movement of Na in NBF polyhedrons. The calculation of the average time between two consecutive jumps and the visiting time for Na atoms leads to the correlation effect for the diffusion of Na atoms. This effect depends on the temperature of the samples.