Perturbation theories for the calculation of molecular interaction energies. I. General formalism
Perturbation theories for the calculation of molecular interaction energies. I. General formalism
复制标题
用于计算分子相互作用能的微扰理论。
DOI：
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发表时间：
1973
期刊：
影响因子：
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通讯作者：
J. Hirschfelder
中科院分区：
文献类型：
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作者：
D. Chipman;J. Bowman;J. Hirschfelder
在计算两个原子的相互作用能时，特别方便的是把零级哈密顿量H（0）取为原子哈密顿量之和。则H（0）不反映精确哈密顿量H的完全置换对称性。许多不同的微扰展开与这样的"非对称“H（0）已被提出。在本文中，这些扩展的审查和分类在一个非常一般的扰动框架。此外，提出了一种新的“优化”方法，凭借Rayleigh-Ritz变分原理，保证比以前提出的任何方法都能得到更好的结果。为了简单起见，分析仅限于无自旋零级函数φ（0）和无自旋精确波函数φ都是非简并的情况。作为一个例子，在每一种方法的一阶波函数的建设进行了详细的讨论，为一个简单的情况下，一个单一的对称操作。
In the calculation of the interaction energy of two atoms, it is particularly convenient to take the zero order Hamiltonian H(0) to be the sum of the atomic Hamiltonians. Then H(0) does not reflect the full permutational symmetry of the exact Hamiltonian H. Many different perturbation expansions with such a ``nonsymmetric' H(0) have been proposed. In this paper, these expansions are reviewed and classified within a very general perturbation framework. Also, a new ``optimized' method is proposed which, by virtue of the Rayleigh‐Ritz variational principle, is guaranteed to give better results than any of the previously suggested methods. For simplicity the analysis is restricted to the case that the spin‐free zero order function φ(0) and the spin‐free exact wavefunction ψ are both nondegenerate. As an example, the construction of the first order wavefunction in each method is discussed in detail for the simple case of a single symmetry operation.