二硅烯及其相关分子的量子化学计算研究

The Calulating Studies of Quantum Chemistry on Disilene and the Related Molecules

使用密度泛函法、MP2法和考虑组态相关作用的QCISD和CCD法,对重主族双键化合物二硅烯、二锗烯等进行了优化构型的量子化学计算.计算结果表明,H2X=XH2(X=Si,Ge,Sn,Pb)型分子均为非平面反式弯曲几何构型,亚甲基XH2的基态为单线态.利用计算的"单线态-三线态"能量差ΔEST和双键键能Eσ+π分析并解释了非平面反式弯曲几何构型的形成条件和标题物中双键的相对强度.

The disilene,digermene and the related molecules that with double bonds between heavier main group elements are calculated by using the density functional theory and MP 2 method.The configuration interaction calculation were peformed with the QCISD and CCD methods,the geometries of molecules were optimized.The calculated results show that transbent distortion occurs in H 2X=XH 2(X=Si,Ge,Sn,Pb) and the carbenoid fragments XH 2 have a singlet ground.The condition of tran bent geometries and the X=X double bonds strength were analysed and interpreted by using the singlet triplet speparation ΔE ST and the X=X σ+π bond energy E σ+π .