The size consistency of multi-reference Møller–Plesset perturbation theory
The size consistency of multi-reference Møller–Plesset perturbation theory
复制标题
多参考Møller-Plesset微扰理论的尺寸一致性
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
P. Pulay
中科院分区：
文献类型：
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作者：
H. V. Dam;J. ;P. Pulay
研究了多参考Moller-Plesset微扰理论的大小一致性与零阶哈密顿量结构的关系。在计算中，它表明，选择的投影算子定义的零阶哈密顿量是至关重要的。实质上，只要这样的投影算子可以写成特定子空间上的投影算子之和，叉积项就可能出现在零阶哈密顿量中，破坏大小的一致性。这个问题可以使用针对跨越激励水平的每个子空间的单独的投影算子来解决。原则上，基于这些投影算子的零阶哈密顿量导致大小一致的微扰理论。然而，人们发现一些非局域自旋重耦合效应仍然存在。一个新的零阶哈密顿最近制定规避这个问题，并显示出完全大小一致。除了投影算符的选择外，激发态的正交化也是关键。
The size consistency of multi-reference Moller–Plesset perturbation theory as a function of the structure of the zeroth-order Hamiltonian is studied. In calculations it is shown that the choice of projection operators to define the zeroth-order Hamiltonian is crucial. In essence whenever such a projection operator can be written as the sum of projection operators onto particular subspaces, cross-product terms may appear in the zeroth-order Hamiltonian that spoil the size consistency. This problem may be solved using a separate projection operator for each subspace spanning an excitation level. In principle a zeroth-order Hamiltonian based on these projection operators results in a size consistent perturbation theory. However, it was found that some non-local spin recoupling effects remain. A new zeroth-order Hamiltonian formulated recently circumvents this problem and is shown to be exactly size consistent. Apart from the choice of projection operators, the orthogonalization of the excited states is cruci...