Development and Application of Electron Correlation Theory Suitable for Molecular Interaction Study

发展了基于局部投影分子轨道(LPMO PT)的微扰理论来研究弱非共价分子相互作用。LPMO PT通过去除轨道基团和构型不一致性，成功地避免了基组叠加误差(BSSE)。使用OpenMP将耗时的部分并行化，最新版本的程序使我们能够有效地计算(H2O)25与aug-cc-pVDZ基组的结合能。计算的(H2O)n(n=6，8，13，20和25)异构体的相对结合能与用更复杂和计算要求更高的方法计算的结果一致。LPMO PT的优点之一是，对于大尺寸分子中的每一对分子，电荷转移项和色散项的能量贡献都可以计算出来。利用这些条件，分析了水团簇中的氢键网络。

The perturbation theory based on the Locally Projected Molecular Orbitals (LPMO PT) was developed to study the weak non-covalent molecular interaction. The LPMO PT successfully avoids the basis set superposition error (BSSE) by removing the orbital basis and configuration inconsistencies. Using the openMP, the time-consuming parts of the codes were parallelized, and the latest version of the code enables us to efficiently compute the binding energy of (H2O)25 with the aug-cc-pVDZ basis set. The calculated relative binding energies of the isomers of (H2O)n (n=6, 8, 13, 20 and 25) agree with those calculated with the more sophisticated and computation-demanding methods. One of the advantages of the LPMO PT is that the energy contribution from the charge-transfer and dispersion terms can be evaluated for every pair of the molecules in the large size of molecules. By utilizing these terms, the hydrogen bonded networks in water clusters are analyzed.