Revisitation of Nonorthogonal Spin Adaptation in Coupled Cluster Theory.
Revisitation of Nonorthogonal Spin Adaptation in Coupled Cluster Theory.
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重新审视耦合簇理论中的非正交自旋适应。
DOI：
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发表时间：
2013
影响因子：
5.5
通讯作者：
J. Stanton
中科院分区：
文献类型：
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作者：
D. Matthews;J. Gauss;J. Stanton
相对于正交自旋适应、自旋轨道和自旋集成理论，讨论了耦合簇方程的非正交自旋适应、自旋自由或轨道表示的好处。特别是，轨道簇振幅的特定线性组合，表示自旋和振幅，被证明可以减少必须明确执行的收缩次数，并简化表达式及其推导。讨论了自旋求和法的计算效率，并与正交自旋适应法和自旋集成法进行了比较。与CCSDT和CCSDTQ的其他方法相比，自旋求和方法具有显著的计算优势。
The benefits of what is alternatively called a nonorthogonally spin-adapted, spin-free, or orbital representation of the coupled cluster equations is discussed relative to orthogonally spin-adapted, spin-orbital, and spin-integrated theories. In particular, specific linear combinations of the orbital cluster amplitudes, denoted spin-summed amplitudes, are shown to reduce the number of contractions that must be explicitly performed and to simplify the expressions and their derivation. The computational efficiency of the spin-summed approach is discussed and compared to orthogonally spin-adapted and spin-integrated approaches. The spin-summed approach is shown to have significant computational advantages relative to the other methods for CCSDT and CCSDTQ.