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

1)对于由闭壳层分子组成的团簇，基于局域投影分子轨道理论（LP MO）建立了MP2水平的理论，并编写了计算机程序。一些测试计算显示出有希望的结果：a）计算的结合能与电荷转移项接近平衡校正的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）考察了单电子性质的基组叠加误差（BSSE），并与LP MO MP2（CT）进行了比较。结果表明，在大多数情况下，BSSE比结合能的BSSE要小。3）利用投影算符，在不考虑正交性条件的情况下，导出了闭壳层和高自旋开壳层分子轨道系数的定态条件，并提出了求解方程的方法。4）推导了由一个开壳层分子和多个闭壳层分子组成的高自旋开壳层团簇的LP MO方程，并进行了编码。5）用LP MO方法和MP2方法研究了离子团簇M^+（Ar）_n（M=Li，Na，K）。通过考察优化的几何构型和势能面，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.