Second-order Moller-Plesset calculations on the water molecule using Gaussian-type orbital and Gaussian-type geminal theory

摘要

The Gaussian-type orbital and Gaussian-type geminal (GGn) model is applied to the water molecule, at the level of second-order Moller-Plesset (MP2) theory. In GGn theory, correlation factors are attached to all doubly-occupied orbital pairs (GGO), to all doubly-occupied and singly-excited pairs (GG1), or to all orbital pairs (GG2). Optimizing the GG2 model using a weak-orthogonality functional, we obtain the current best estimate of the all-electron MP2 correlation energy of water, —361.95 mE_h. In agreement with previous observations, the GG1 model performs almost as well as the GG2 model (—361.26 mE_h), whereas the GGO model is poorer (—351.36 mE_h). For the barrier to linearity of water, we obtain an MP2 correlation contribution of —463 ± 5 cm~(-1).