Effect of Negative Pressure on the Structure and Diffusion Process of Silicon Dioxide at a Liquefied Nitrogen Temperature Using Molecular Dynamics Simulations

Abstract

This study uses molecular dynamics (MD) simulations to investigate the effect of negative pressure on the structure and diffusion process of SiO_x structural units (x = 4, 5) in Silicon dioxide at a liquefied nitrogen temperature. When decreases the pressure from 0 GPa to -10 GPa at 70 K, the lengths of the links Si-Si, Si-O, and O-O initially increase and then decrease, the system size increases, and the total energy of the system increases. During the diffusion process, number of structural units SiO₄ increases, whereas the number of structural units SiO₅ decreases. The average coordination number of link Si-O is constantly 4.0, while the average coordination number of link O-O decreases from 7.0 to 6.0, leading to changes in the microstructural characteristics. This is accompanied by changes in bond angles, with SiO₄ has is 105 (degree) and SiO₅ decreasing from 90 (degree) to 85 (degree). The length of the links increases from 1.64 Å to 1.66 Å for number of structural units SiO₄ and increases from 1.68 Å to 1.74 Å for SiO₅ units. These findings provide a basis for future experimental studies aimed at the research and development of advanced materials.