Al_2O_3X_2(X=H,D,T)的电子振动近似方法

Electron-vibration approximate method for hydrogen isotope compounds Al_2O_3X_2(X = H,D,T)

用密度泛函理论在B3LYP/6-311++g(d,p)基组水平上对Al_2O_3X_2(X=H,D,T)分子的可能较低能量构型进行了几何优化.结果表明该分子的基态电子态和对称性为Al_2O_3X_2(X=H,D,T)(~1A′)C_s,计算了氢同位素分子及Al_2O_3X_2(X=H,D,T)的电子能量E、定容热容C_V和熵S.用电子振动近似方法计算了固体Al_2O_3的氢化热力学函数△H^0,△S^0,△G^0,以及平衡压力与温度的关系.当Al_2O_3吸附氢(氘,氚)形成固体时,反应的氢氘氚排代效应的顺序为氚排代氘,氘排代氢,与钛等金属与氢及其同位素反应的氢氘氚排代效应的顺序相反.总体来说,这种排代效应都非常弱.随着温度的增加,这系列反应的氢氘氚排代效应趋于消失.

The geometric configurations, vibration frequencies and thermodynamics properties of A12O3X2 （X = H, D, T） molecular clusters with lower energy are optimized using the B3LYP/6-311＋＋g （d, p） method. The changes of entropy, enthalpy and Gibbs free energy of the reactions between A12O3 and hydrogen （deuterium or tritium） gas are calculated by the solid electron-vibration approximate method and thermodynamic formulae at temperatures of 298, 398, 498, 598, 698, 798, 898, 998 and 1098 K, and then the relationships between the equilibrium pressure of hydrogen （deuterium or tritium） gas and temperature in these reactions are obtained. The results show that the ground state of the gaseous A1203H2 is Al^O3X2 （X ---- H, D, T） （1A＇） C~. Hydrogen can be displaced by deuterium; deuterium can be displaced by tritium in the reactions between A12Oa and X2 with the productions of solid A1203X2 which relates to ground gaseous A12OaX2 with Cs symmetry. This displacement sequence is opposite to that in the reactions between titanium and X2. These displacement effects are very weak, and they are weaker and weaker as the temperature increases.