基于密度泛函理论的CO_(2)分子动力学研究

Molecular Dynamics of CO_(2) Based on Density Functional Theory

采用CP2K程序中的QUICKSTEP模块,以密度泛函理论为基础,采用广义梯度近似下的PBE泛函,模拟CO_(2)气体分子扩散,完成分子动力学微观机理探究。模型构建80个CO_(2)气体分子,晶胞边界为20A×20A×20A,计算CO_(2)气体分子在300K、500K和700K温度条件下的扩散系数。在优化过程中,分析CO_(2)气体分子的键长、键角和势能的变化,以及对应条件下的均方位移和径向分布函数。计算结果表明,在整个扩散过程中,CO_(2)气体键角变化要强于键长变化,CO_(2)气体分子的均方位移斜率随着温度的增加而增加,扩散系数随着温度的增加而增加;径向分布函数计算结果表明,C原子周围的O配位数为2,且C和O原子之间并未有电子交换现象,C原子之间发生了电子交换,O原子之间也发生了一定的电子交换,但是其配位距离较远,发生电子的交换作用较弱。

In this paper,QUICKSTEP module in CP2K program was adopted.Based on density functional theory,PBE functional under generalized gradient approximation was used to simulate the molecular diffusion of CO_(2)gas and explore the microscopic mechanism of molecular dynamics.The model constructed 80 CO_(2)gas molecules with cell boundaries of 20A×20A×20A,and calculated the diffusion coefficients of CO_(2)gas molecules at 300K,500K and 700K temperatures.In the optimization process,the changes of bond length,bond Angle and potential energy of CO_(2)gas molecules,as well as the mean azimuth shift and radial distribution function under corresponding conditions are analyzed.The results show that the change of CO_(2)gas bond Angle is stronger than that of bond length during the whole diffusion process.The mean azimuth shift slope of CO_(2)gas molecules increases with the increase of temperature,and the diffusion coefficient increases with the increase of temperature.The calculation results of the radial distribution function show that the O coordination number around the C atom is 2,and there is no electron exchange between the C atom and the O atom,but there is electron exchange between the C atom and a certain amount of electron exchange between the O atom,but the coordination distance is far away,and the electron exchange is weak.