CO2二聚体分子弱结合作用的DFT计算

用密度泛函理论(DFT)的Becke 3LYP方法,在不同基集合（6 31G和6 311G系列）下对平行结构（C 2h）和T形结构(C2v)的CO2二聚体进行ab initio计算.通过计算,得到了CO2二聚体C2h和C2v两种构型的结构参数和离解能,并给出了CO2二聚体相对稳定构型C2h的12个正则振动分析图.结果表明,CO2二聚体的离解能为2 kJ•mol－1,CO2分子之间振动频率很小,从而说明CO2二聚体是弱结合分子.

Calculation on Weakly Bound Carbon Dioxide Dimer by DFT

It is predicted that there are two geometrical configurations of the slipped parallel (C2h) and T shaped (C2v) carbon dioxide dimer using the density functional theory(DFT) with basis sets 6-31G or 6-311G.The normal vibration analysis has showed 12 vibrational modes for C2h,which can be classified in three types ,i.e.ν 11(bu),ν 1(ag),ν 9(bu)and ν 4(ag) contributed mainly by intramolecular stretching vibrations,ν 8(bg),ν 12(bu),ν 6(au) and ν 5(ag) contributed mainly by intramolecular bending vibrations,and ν 7(au),ν 10(bu),ν 2(ag) and ν 3(ag) provided by intermolecular vibrations with frequencies 20～ 100 cm－ 1.The (CO2)2 is a typical weakly bound molecule based on its small dissociation energy 2 kJ· mol－ 1 and normal vibration modes.