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arXiv 1904.08093physics.chem-phcond-mat.str-el
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具有复杂自旋限制轨道的Kohn-Sham密度泛函理论:一类新的无对称性困境的密度

Kohn-Sham Density Functional Theory with Complex, Spin-Restricted Orbitals: Accessing a New Class of Densities without the Symmetry Dilemma

Joonho Lee, Luke W. Bertels, Martin Head-Gordon

摘要:

我们表明,使用复杂的,自旋限制轨道(CR)在科恩-沙姆密度泛函理论(KS-DFT)允许一个访问一个新的一类的密度,是不可访问的自旋限制(RKS)或自旋非限制(UKS)轨道。进一步证明了当密度矩阵的虚部不为零时,cRKS密度矩阵的实部可以是非幂等的.使用cRKS轨道显示了SPW 92、PBE、BLYP和TPSS泛函的TS 12基准集的三重态-单重态间隙的显著改善。此外,它表明,RKS和UKS产生定性错误的电荷密度和自旋密度,分别导致更差的能量。我们证明了现代泛函SCAN,MN 15-L和B 97 M-V即使在cRKS轨道的定性更准确的密度下也没有显示出令人惊讶的改进。为此,我们的工作不仅铺平了道路,以逃避对称性困境时,存在一个cRKS解决方案,但也提出了一个新的路线,以设计更好的近似XC泛函。

英文摘要:

We show that using complex, spin-restricted orbitals (cR) in Kohn-Sham density functional theory (KS-DFT) allows one to access a new class of densities that is not accessible by either spin-restricted (RKS) or spin-unrestricted (UKS) orbitals. We further show that the real part of a cRKS density matrix can be non-idempotent when the imaginary part of the density matrix is not zero. Using cRKS orbitals shows significant improvements in the triplet-singlet gaps of the TS12 benchmark set for the SPW92, PBE, BLYP, and TPSS functionals. Moreover, it was shown that RKS and UKS yield qualitatively wrong charge densities and spin densities, respectively, leading to worse energetics. We demonstrate that the modern functionals SCAN, MN15-L, and B97M-V show surprisingly no improvement even with a qualitatively more accurate density from cRKS orbitals. To this end, our work not only paves the way to escape the symmetry dilemma whenever there exists a cRKS solution, but also suggests a new route to design better approximate XC functionals.

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