Simulation Study On The Adsorption And Diffusion Behavior Of Small Molecules On The[1-trimethylsilyl-1-propyne]and Cu₂O Surface

This study investigates the permeation behavior of small molecule in polymer and the sorption and decomposition dynamics process of gases molecules on metal oxide surface using molecular dynamics and first principle calculations. The main contents include two aspects:first, the solution and diffusion behavior of small molecules in Poly [1-trimethylsilyl-1-propyne] (PTMSP); second, the sorption and decomposition dynamics process of H2S on Cu2O(111).For one thing, molecular dynamics simulation and Grand canonical Monte Carlo (GCMC) simulation are used to investigate the performance of PTMSP membrane for organic vapor/ permanent-gas separation. In general, the calculated diffusion and solubility coefficients of permanent gases and organic vapors in PTMSP are consistent with the experimental data, and correlate well with the square of the effective molecule diameter and critical temperature of each penetrant molecule. The simulation results reveal that the high organic-vapor/permanent-gas permeability selectivity of PTMSP can be attributed to the high organic-vapor/permanent-gas solubility selectivity. A comprehensive microscopic interpretation is provided based on the analysis of the center-of-mass displacements of penetrant molecules and the study of the free-volume size and distribution in PTMSP.Also, Density functional theory calculations have been applied to study the adsorption and decomposition of H2S on Cu2O (111). We investigate the site preference of H2S and other intermediates, SH, S and H on Cu2O (111). H2S is found to weakly molecularly adsorbed on Cucsa site. However, SH and S are found to be strongly chemisorbed on Cu2O (111), with S atoms bind to nearby two Cucus atoms and one Cucsa atom forming pyramid structure. Isolated H atom is predicted to bind strongly with Cucus site. The minimum energy paths for H2S and SH dehydrogenation are determined. The H2S(ad)â†'SH(ad)+H(ad) reaction is found to have low barrier and median exothermicity. However, the SH(ad)â†'S(ad)+H(ad) reaction is not a very facile process, and SH may stably exist on Cu2O (111)This study provides theoretical support for the permeation process of small molecules in polymer membrane and poisonous mechanism of industrial catalysts.