Decomposition of the Electronic Energy in Terms of Density, Density Coherence, and the Connected Part of the Two-Body Reduced Density Matrix
Decomposition of the Electronic Energy in Terms of Density, Density Coherence, and the Connected Part of the Two-Body Reduced Density Matrix
复制标题
电子能量的密度分解、密度相干性和二体约化密度矩阵的连通部分
DOI：
10.1021/acs.jctc.1c00679
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发表时间：
2021
影响因子：
5.5
通讯作者：
Truhlar, Donald G.
中科院分区：
文献类型：
--
作者：
Zhang, Dayou;Truhlar, Donald G.
通过对用Hartree-Fock理论、完全活性空间自洽场（CASSCF）理论和多参考组态相互作用（MRCI）计算的电子能量进行分解，分析了静态和动态电子关联。我们使用了三种不同的方案来分解H2、F2和N2解离势能曲线的相对能量贡献。第一个分解方案涉及能量的经典和非经典分量。第二个和第三个认识到能量中无法用一体约化密度矩阵表示的部分;这被称为连接能量。非连通分量被进一步分解为可从密度计算的部分和可从密度相干性计算的部分。第一个分解方案表明，一个电子的能量和经典的两个电子的能量的总和包含一个可以忽略不计的静态相关的部分。这一数量在三个级别之间的差异相对较小，特别是对于CASSCF和MRCI。这解释了为什么多组态对密度泛函理论和多组态密度相干泛函理论能够提高CASSCF能量。后两个分解表明，连接的能量包含一个显着的静态相关的一部分。在这三个水平上，密度或密度相干性所代表的能量是显著不同的。混合不同方法之间的密度和密度相干性可能导致键离解能和平衡键距的系统误差，表明密度能量分量和密度相干能量分量都包括大量的静态和动态相关性。这些波函数分解可以是有用的发展新的泛函密度泛函理论，密度相干泛函理论，密度矩阵泛函理论，对密度泛函理论和指导这些理论的期望。
We analyzed static and dynamic electron correlation by decomposing the total electronic energy of calculations by restricted Hartree–Fock theory, complete active-space self-consistent field (CASSCF) theory, and multireference configuration interaction (MRCI). We used three different schemes to break down the relative energy contributions to the potential energy curves for the dissociation of H2, F2, and N2. The first decomposition scheme involves the classical and nonclassical components of the energy. The second and third recognize the part of the energy that is not expressible in terms of the one-body reduced density matrix; this is called the connected energy. The unconnected component is further decomposed into a part calculable from the density and the part calculable from the density coherence. The first decomposition scheme shows that the sum of the one-electron energy and the classical two-electron energy contains a negligible portion of the static correlation. This quantity has a relatively small variance between the three levels, especially for CASSCF and MRCI. This provides an explanation of why multiconfiguration pair-density functional theory and multiconfiguration density-coherence functional theory are able to improve the CASSCF energy. The latter two decompositions show that the connected energy contains a significant portion of static correlation. The energy representable by either the density or the density coherence is significantly different at the three levels. Mixing the density and density coherence between different methods may lead to a systematic error in the bond dissociation energy and the equilibrium bond distance, indicating that the density energy component and the density coherence energy component both include a significant amount of both static and dynamic correlation. These wave function decompositions can be useful for developing new functionals for density functional theory, density-coherence functional theory, density matrix functional theory, and pair-density functional theory and for guiding expectations for these theories.