中文摘要：

利用超分子二阶到四阶多体微扰理论和扩展的相关一致基组（aug-cc-pVTZ）结合有效的中点键函数（3s3p2d1f1g）计算水二聚物的平衡结构和分子间相互作用势，并用平衡方法修正基组重叠误差．在MP2／aug-cc-pVTZ理论级别优化水二聚物几何构型．与正常优化的结果相比，平衡修正优化得到的Ro—o和α值分别轻微的增加0．002nm和0．19°，同时，θ值减小0．013°．在MP2水平利用扩展的相关一致基组结合有效键函数，预言了Ro-o和ΔECP值分别为0．0923nm和-4．86kcal／mol，计算结果与实验值符合得很好．用exp-4．2势函数拟合分子间相互作用能的离散点，拟合结果与从头算计算的结果一致．

英文摘要：

The equilibrium structure and intermolecular interaction potentials of water dimer have been calculated using supermolecular many-body perturbation theory at the second-order to fourth-order levels. The augmented correlation-consistent basis set aug-cc-pVTZ and the effective midbond functions {3s3p2d1f1g} are employed. Basis set superposition error is corrected by applying the counterpoise procedure. At the MP2 level with aug-cc-pVTZ basis set, the values of Ro-o and a slightly increase 0. 002 nm and 0.19°, respectively, while the magnitude of 0 drops 0. 013° on the CP-optimization geometry compared with the normal optimization geometry. The MP2 calculations with augmented correlation-consistent basis set combining with effective midbond functions predict the values of Ro_o, and ΔECP, for 0. 293 nm and -4.86 kcal/mol respectively, which are in better agreement with experiment. The discrete grid of calculated intermolecular interaction energies is fitted to exp - 4.2 potential function. The agreement between the fitting and the ab initio results is excellent.