致密气在α-SiO2（010）面吸附的第一性原理研究
First-principles calculation of adsorption for tight gas on α-SiO2(010) surface

致密气在砂岩储层中的赋存状态一直是人们研究的热点. 为了论证致密气在石英砂岩表面吸附性的强弱，基于密度泛函理论的第一性原理方法，以CH4分子为主要研究对象，研究了CH4、C2H6、CO2、N2分子在α-SiO2（010）面的吸附性质. 结果表明：CH4、C2H6、CO2、N2分子在α-SiO2（010）面的吸附能力从小到大依次为CO2
The occurrence of tight gas in sandstone reservoirs has been a hot topic. To demonstrate the adsorption strength of tight gas on the quartz sandstone surface, the adsorptions of CH4, C2H6, CO2 and N2 molecules on α-SiO2 (010) surface have been studied, respectively, by using first principles method based on the density functional theory (DFT). The results show that the adsorption capacity of CH4, C2H6, CO2 and N2 molecules on α-SiO2 (010) surface from small to large is in turn: CO2, N2, CH4 and C2H6. The lowest adsorption energy -0.5379eV and minimal geometric change of CH4 molecule is at B12 site, where the adsorption is the most stable and it belongs to physical adsorption. The adsorption of hydrocarbon gases is stronger than that of non hydrocarbons. The adsorption energy changes small at different adsorption sites, which indicates that gases are easy to move on α-SiO2 (010) surface; After adsorption at B12 site, the partial density of states (PDOS) curves of CH4 molecule are shifted to the lower energy region about 3.2 eV, while the curves of silicon atoms in α-SiO2 (010) surface are basically coincident.