The IMOMO method: Integration of different levels of molecular orbital approximations for geometry optimization of large systems: Test for n-butane conformation and S(N)2 reaction: RCl+Cl-
The IMOMO method: Integration of different levels of molecular orbital approximations for geometry optimization of large systems: Test for n-butane conformation and S(N)2 reaction: RCl+Cl-
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DOI：
10.1063/1.472065
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发表时间：
1996-08-01
影响因子：
4.4
通讯作者：
Morokuma, K
中科院分区：
文献类型：
--
作者：
Humbel, S;Sieber, S;Morokuma, K
提出了两种不同层次MO逼近的积分方法。只有分子的活性部分或较难的部分在较高的近似水平上处理，而分子的其余部分在较低的近似水平上处理。通过三种不同的计算定义了总能量和能量导数的积分，利用积分能量可以优化过渡态结构和平衡结构。任何分子轨道近似的任何组合（从头算，密度泛函到半经验）都可以使用。对乙烷和正丁烷的构象能以及乙基、丙基、异丁基和新戊酰氯与Cl-的S(N)2反应进行了试验计算，并与常规MO计算进行了比较。结果表明，这些方法在大分子，特别是过渡态的理论研究中具有巨大的潜力。(C) 1996年美国物理研究所。
A integration of two different levels of MO approximation is presented. Only the active or more difficult part of a molecule is treated at a higher level of approximation and the rest of the molecule at a lower level of approximation. The integrated total energy and energy derivatives are defined from three different calculations, and the structure of transition state as well as the equilibrium structure can be optimized using the integrated energy. Any combination of any molecular orbital approximations (ab initio, density functional to semi-empirical) can be used. Test calculations in the IMOMO method have been performed and compared with normal MO calculations for the conformation energy of ethane and n-butane and the S(N)2 reaction of ethyl, propyl, isobutyl, and neopentyl chloride with Cl-. The results indicate that these methods have a tremendous potential for theoretical study of larger molecules, in particular for transition states. (C) 1996 American Institute of Physics.