气体在玻璃中渗透的数值模拟

To understand the penetration mechanism of ambient gases in glass shell materials of ultra-high vacuum electronic devices in depth, numerical simulation of gas permeation including dissolution and diffusion processes in glass was studied with the methods of giant canonical Monte Carlo and molecular dynamics. The solubility coefficients of oxygen, helium, hydrogen and water vapor molecules in two kinds of glass structure, together with the diffusion coefficients, permeability coefficients and motion trajectories of oxygen and hydrogen molecules in soda-lime glass, were calculated based on the COMPASS (Condensed-phase optimized molecular potentials for atomistic simulation studies) force field. The calculation results show that a kind of gas having a higher affinity with glass has a higher solubility coefficient. Metal ions distributed in glass make the size of pores in glass smaller, which results in a lower gas solubility coefficient of soda-lime glass. Both of rising environment temperature and gas pressure can push up the diffusion and permeability coefficients of gases. During the diffusion process, most of the time gas molecules vibrate in certain positions and occasionally jump once, which makes gas molecules gradually apart from their initial positions. H₂ molecules have a higher diffusion coefficient compared with larger O₂ molecules because glass can provide more effective diffusion channels for gas molecules with smaller size. The research results can provide theoretical bases for exploring the vacuum failure mechanism of ultra-high vacuum electronic devices and optimizing the material and structure of glass shells used in devices.