Multiconfiguration Pair-Density Functional Theory
Multiconfiguration Pair-Density Functional Theory
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DOI：
10.1021/ct500483t
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发表时间：
2014-09-01
影响因子：
5.5
通讯作者：
Gagliardi, Laura
中科院分区：
文献类型：
--
作者：
Li Manni, Giovanni;Carlson, Rebecca K.;Gagliardi, Laura
我们提出了一个新的理论框架，称为多组态对密度泛函理论（MC-PDFT），它结合了多组态波函数与广义的密度泛函理论（DFT）。一个多组态自洽场（MCSCF）波函数与正确的自旋和空间对称性被用来计算总的电子密度，其梯度，在顶部的对密度，以及动能和库仑贡献的总电子能量。然后，我们使用总密度，其梯度和上对密度的泛函来计算能量的剩余部分，我们称之为上密度泛函能量，与KohnSham DFT的交换相关能量相反。因为顶对密度是双粒子密度矩阵的一个元素，这超出了只涉及单粒子密度的霍恩伯格-科恩定理。为了说明这个理论，我们获得第一近似所需的新类型的密度泛函通过翻译传统的密度泛函的自旋密度使用一个简单的处方，我们进行后SCF密度泛函计算使用的总密度，密度梯度，和顶部对密度从MCSCF计算。动态相关或交换的双重计数不会发生，因为不使用MCSCF能量。该理论通过应用于H-2、N-2、F-2、CaO、Cr-2和NiCl的键能和势能曲线以及Be、C、N、N+、O、O+、Sc+、Mn、Co、Mo、Ru、N-22、HCHO、C_4H_6、c-C_5 H_6和吡嗪的电子激发能来说明。所提出的方法具有类似于MCSCF的计算成本和缩放，但定量的准确性，即使与目前的第一近似的新类型的密度泛函，这是比较昂贵的多参考微扰理论方法。
We present a new theoretical framework, called Multiconfiguration Pair-Density Functional Theory (MC-PDFT), which combines multiconfigurational wave functions with a generalization of density functional theory (DFT). A multiconfigurational self-consistent-field (MCSCF) wave function with correct spin and space symmetry is used to compute the total electronic density, its gradient, the on-top pair density, and the kinetic and Coulomb contributions to the total electronic energy. We then use a functional of the total density, its gradient, and the on-top pair density to calculate the remaining part of the energy, which we call the on-top-density-functional energy in contrast to the exchange-correlation energy of KohnSham DFT. Because the on-top pair density is an element of the two-particle density matrix, this goes beyond the HohenbergKohn theorem that refers only to the one-particle density. To illustrate the theory, we obtain first approximations to the required new type of density functionals by translating conventional density functionals of the spin densities using a simple prescription, and we perform post-SCF density functional calculations using the total density, density gradient, and on-top pair density from the MCSCF calculations. Double counting of dynamic correlation or exchange does not occur because the MCSCF energy is not used. The theory is illustrated by applications to the bond energies and potential energy curves of H-2, N-2, F-2, CaO, Cr-2, and NiCl and the electronic excitation energies of Be, C, N, N+, O, O+, Sc+, Mn, Co, Mo, Ru, N-22, HCHO, C4H6, c-C5H6, and pyrazine. The method presented has a computational cost and scaling similar to MCSCF, but a quantitative accuracy, even with the present first approximations to the new types of density functionals, that is comparable to much more expensive multireference perturbation theory methods.