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

This study uses molecular dynamics (MD) simulations to investigate the effect of negative pressure on the structure and diffusion process of SiOx 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.