Development of a new molecular orbital theory for avoiding the basis set superposition error in the molecular interaction energy

1)针对由封闭壳层分子组成的团簇，建立了基于局部投影分子轨道理论（LP MO）的MP2级理论，并编写了计算机代码。一些测试计算显示了有希望的结果；a)带电荷转移项的计算结合能接近平衡校正的SCF结合能。b)色散交换项对结合能的贡献很大，特别是在势能最小值附近。2)检测了单电子性质的基集叠加误差（BSSE），并与LP MO MP2（CT）进行了比较。结果表明，在大多数研究的例子中，BSSE没有结合能那么严重。3)利用投影算子，导出了不存在正交性条件的闭壳层和高自旋开壳层分子轨道系数的平稳条件，并给出了方程的求解方法。本文推导了由一个开壳分子和多个闭壳分子组成的高自旋开壳团簇的LP - MO方程，并正在进行编码。5)采用LP MO法和MP2法对离子簇M^+(Ar)_n （M=Li,Na，K）进行了研究。通过考察优化后的几何形状和势能面，分析了相互作用项。

1)For the clusters consisting of the closed shell molecules, the MP2 level of theory based on the locally-projected molecular orbital theory (LP MO) was developed, and the computer codes were written. A few test calculations showed promising results ; a)the calculated binding energy with the charge-transfer terms is close to the counterpoise corrected SCF binding energy. b)The dispersion-exchange term contributes substantially to the binding energy, particularly near the potential energy minimum.2)The basis set superpose error(BSSE) for the one-electron properties are examined, and are compared with the LP MO MP2(CT). It turns out that the BSSE is less serious than for the binding energy in most of the examples examined.3)Using the projection operators, the stationary condition for closed shell and high-spin open shell molecular orbital coefficients is derived without the orthogonality condition, and a method to solve the equation is proposed. It can be an alternative and direct method to obtain the localized molecular orbitals4)The equations of LP MO for the high-spin open shell cluster, which consists of one open shell molecule and many closed shell molecules, is derived, and the coding is under development.5)With LP MO method and MP2 method, the ionic clusters, M^+(Ar)_n (M=Li,Na,K) were studied. By examining the optimized geometries and the potential energy surfaces, the interaction terms are analyzed.