The structure and dynamic in network forming liquids: molecular dynamic simulation

Abstract

The structure and dynamic in network-forming liquids has been investigated by mean of molecular dynamics simulation. Several models consisting of 1,998 or 2,000 atoms for silica and alumina liquids respectively were constructed under a wide pressure range and at temperature of 3,000 K. The local structure is analysed through the void and topology statistics. It was found that the structure of considered liquids comprises D4, D5 and D6 domains which consist of units TOx (x = 4, 5 and 6; T is Si or Al). The volume occupied by all voids and the volume of all models can be expressed as a linear function of the fraction of units TOx indicating the three domain structure. The densification of liquids is performed with varying the volume of those domains. As regards to dynamic, the simulation also demonstrates the linear relationship between diffusion constant and the fractions of units TOx. Furthermore, we found that the diffusion anomaly occurred in silica liquids is caused by very high mobility of silicon and oxygen in the D5 domain compared to one in other domains.