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Spin-state dependence of exchange-correlation holes.
Faraday Discussions ( IF 3.3 ) Pub Date : 2020-06-11 , DOI: 10.1039/d0fd00060d Julia Brüggemann 1 , Christoph R Jacob
Faraday Discussions ( IF 3.3 ) Pub Date : 2020-06-11 , DOI: 10.1039/d0fd00060d Julia Brüggemann 1 , Christoph R Jacob
Affiliation
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Applications of density-functional theory (DFT) in computational chemistry rely on an approximate exchange–correlation (xc) functional. However, existing approximations can fail dramatically for open-shell molecules, in particular for transition-metal complexes or radicals. Most importantly, predicting energy differences between different spin-states with approximate exchange–correlation functionals remains extremely challenging. Formally, it is known that the exact xc functional should be spin-state dependent, but none of the available approximations feature such an explicit spin-state dependence [C. R. Jacob and M. Reiher, Int. J. Quantum Chem., 2012, 112, 3661–3684]. Thus, to find novel approximations for the xc functional for open-shell systems, the development of spin-state dependent xc functionals appears to be a promising avenue. Here, we set out to shed light on the spin-state dependence of the xc functional by investigating the underlying xc holes, which we extract from configuration interaction calculations for model systems. We analyze the similarities and differences between the xc holes of the lowest-energy singlet and triplet states of the dihydrogen molecule, the helium atom, and the lithium dimer. To shed further light on the spin-state dependence of these xc holes we also discuss exact conditions that can be derived from the spin structure of the reduced two-electron density matrix. Altogether, our results suggest several possible routes towards the construction of explicitly spin-state dependent approximations for the xc functional.
中文翻译：
交换相关孔的自旋状态依赖性。
密度泛函理论（DFT）在计算化学中的应用依赖于近似交换相关（xc）泛函。但是，对于开壳分子，特别是对于过渡金属配合物或自由基，现有的近似方法可能会严重失败。最重要的是，用近似的交换相关函数预测不同自旋状态之间的能量差仍然极具挑战性。正式地，众所周知，确切的xc泛函应该是自旋态相关的，但是没有一个可用的近似方法具有这种明确的自旋态相关性[CR Jacob and M. Reiher，Int。J.量子化学。，2012，112，3661–3684]。因此，为了为开壳系统的xc功能找到新颖的近似值，依赖于自旋态的xc功能的开发似乎是一个有前途的途径。在这里，我们着手研究底层xc孔，以揭示xc功能的自旋态依赖性，这些孔是从模型系统的配置交互计算中提取的。我们分析了二氢分子，氦原子和锂二聚体的最低能量单重态和三重态的xc孔之间的异同。为了进一步阐明这些xc空穴的自旋态依赖性，我们还讨论了可以从还原的双电子密度矩阵的自旋结构得出的确切条件。共，
更新日期：2020-06-11
中文翻译：
交换相关孔的自旋状态依赖性。
密度泛函理论（DFT）在计算化学中的应用依赖于近似交换相关（xc）泛函。但是，对于开壳分子，特别是对于过渡金属配合物或自由基，现有的近似方法可能会严重失败。最重要的是，用近似的交换相关函数预测不同自旋状态之间的能量差仍然极具挑战性。正式地，众所周知，确切的xc泛函应该是自旋态相关的，但是没有一个可用的近似方法具有这种明确的自旋态相关性[CR Jacob and M. Reiher，Int。J.量子化学。，2012，112，3661–3684]。因此，为了为开壳系统的xc功能找到新颖的近似值，依赖于自旋态的xc功能的开发似乎是一个有前途的途径。在这里，我们着手研究底层xc孔，以揭示xc功能的自旋态依赖性，这些孔是从模型系统的配置交互计算中提取的。我们分析了二氢分子，氦原子和锂二聚体的最低能量单重态和三重态的xc孔之间的异同。为了进一步阐明这些xc空穴的自旋态依赖性，我们还讨论了可以从还原的双电子密度矩阵的自旋结构得出的确切条件。共，
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