PH_3…H_2O体系分子间相互作用的从头计算MO研究

Ab initio MO Study on the PH3…H2O Complexes

在MP2/6-311++G(3d,3p)水平,对PH_3…H_2O体系可能存在的氢键复合物进行了全自由度能量梯度优化,发现PH_3…H_2O体系存在三个能量极小结构A,B和C.其中结构A和B以H_2O作为质子授体,结构C以PH_3作为质子授体,结构A较结构B和C分别稳定6.52kJ/mol和8.18kJ/mol.结构A具有C_s对称性,其结构中P原子和O原子间距离为354.78nm,键角∠OHP为171.35°,属于接近于直线的传统型氢键结构.进一步在高级电子相关校正的MP4SDTQ水平下,用6-311++G(3df,3pd)基加上键函数{3s3p2d1f},通过BSSE校正,精确计算了结构A的结合能为-10.84kJ/mol.

The intermolecular geometry of the weak hydrogen - bonded complex PH3…H2O was optimized using the second - order Moller - Plesset perturbation theory (MP2) at 6 - 311 + + G(3d,3p) level. Three equilibrium structures (A, B and C) was found. The geometry A, which exhibits the conventional structural features of a hydrogen - bonded system with H2O as the proton donor, is the most stable one in the three equilibrium structures. Using the geometry A, which has Cs symmetry and R(P…O) = 354.78nm, correlation energy has been calculated with 6-311 + + G(3df,3pd) basis set adding bond function {3s3p2d1f} using MP2, and MP4SDTQ. The computed binding energy is - 10.84 kJ/mol at MP4SDTQ level.