石英玻璃高温分子动力学模拟中的势函数

根据石英玻璃高温下的分子动力学研究, 分析了势函数中多体势在高温应用下的局限性, 认为离子型对势在模拟石英玻璃高温结构方面优于多体势. 在原子电荷转移方面, 计算并分析了Si和O原子电荷大小对计算原子自扩散系数的影响, 发现用原子电荷转移较少的Morse势函数计算的原子自扩散激活温度比BKS势函数计算的低, 而且在同一温度下, 自扩散系数的计算值也随着原子电荷的减小而增大, 因此, 较小的原子电荷转移应该有利于石英玻璃在高温下的动力学性能的研究.

Interatomic Potentials of Silica Glass for Molecular Dynamics Simulation at High Temperature

Multi-body interaction and atomic charge transfer played essential roles in depicting the ionic-covalent bonds of Si—O systems. The limitations of 3-body terms in interatomic potentials for silica glass were analyzed according to molecular dynamics studies at high temperature, and it was found that pair-wise ionic potentials were better in simulating the microstructure evolution of silica glass than multi-body potentials. Moreover, the effects of atomic charge transfer on atomic self-diffusion were investigated, which showed that the activation temperature of atomic self-diffusion calculated with the Morse potential was lower than that calculated with the BKS potential due to the less atomic charge transfer in Morse potential. It was also found that the atomic self-diffusion coefficients calculated increased with the decrease in atomic charge transfer at the same temperature. Therefore, the pair-wise potentials with less atomic charge transfer should be in favor of investigating the dynamic properties of silica glass at high temperature.