Hartree-Fock orbital instability envelopes in highly correlated single-reference wave functions
Hartree-Fock orbital instability envelopes in highly correlated single-reference wave functions
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DOI：
10.1063/1.474178
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发表时间：
1997-12-22
影响因子：
4.4
通讯作者：
Schaefer, HF
中科院分区：
文献类型：
--
作者：
Crawford, TD;Stanton, JF;Schaefer, HF
研究了Hartree-Fock轨道不稳定性对Hartree-Fock和相关理论水平上力常数预测的影响。由于轨道旋转参数的相关能量的二阶导数的二次依赖性，异常的力常数奇异性包围的“不稳定火山”给出了单参考相关方法在这里检查。无限阶耦合簇方法确实受到参考不稳定性的影响，但在一个相当小的区域的潜在的表面，而微扰三重校正往往扩大耦合簇火山。高阶多体微扰理论产生了非常宽的火山，如果感兴趣的几何形状位于参考行列式的不稳定性附近，那么相应的振动谱预测可能会受到严重影响。(C)1997年美国物理学会。
The effects of Hartree-Fock orbital instabilities on force constant predictions at both Hartree-Fock and correlated levels of theory are investigated. Due to the quadratic dependence of the second derivative of correlated energies on the orbital rotation parameters, anomalous force constant singularities enveloped by "instability volcanoes" are given by the single-reference correlation methods examined here. Infinite-order coupled-cluster methods are indeed affected by the reference instability, but over a rather small region of the potential surface, whereas perturbative triples corrections tend to widen the coupled-cluster volcano. Finite-order many-body perturbation theory yields very wide volcanoes, and corresponding predictions of vibrational spectra may be seriously compromised if the geometry of interest lies at all in the vicinity of an instability in the reference determinant. (C) 1997 American Institute of Physics.