Compressed-State Multistate Pair-Density Functional Theory
Compressed-State Multistate Pair-Density Functional Theory
复制标题
DOI：
10.1021/acs.jctc.0c00908
复制
发表时间：
2020-12-08
影响因子：
5.5
通讯作者：
Truhlar, Donald G.
中科院分区：
文献类型：
--
作者：
Bao, Jie J.;Zhou, Chen;Truhlar, Donald G.
多组态对密度泛函理论（MC-PDFT）是一种多参考方法，可用于计算激发态。然而，MC-PDFT势能表面在圆锥交叉处具有错误的拓扑，因为MC-PDFT的最后一步不是模型空间哈密顿矩阵的对角化，例如，在多状态二阶微扰理论（MS-CASPT 2）中所做的。我们以前已经提出了解决这个问题的方法，对角化的模型空间有效的哈密顿矩阵，其中的对角元素是MC-PDFT能量的中间状态，和非对角元素的波函数理论进行评估。以前的一种方法称为变分多态PDFT（VMS-PDFT），其中间状态最大化有效哈密顿量的迹，即模型空间状态的MC-PDFT能量之和; VMS-PDFT是非常鲁棒的，但是比另一种方法，扩展的多态PDFT，在计算上更昂贵（XMS-PDFT），其中不需要任何密度泛函评估就可以完成到中间态的转换。然而，尽管VMS-PDFT在所有测试情况下都是准确的，但XMS-PDFT仅在其中一些情况下是准确的。在本文中，我们提出了一种新的方法，称为压缩状态多状态PDFT（CMS-PDFT），这是一样有效的XMS-PDFT和VMS-PDFT的准确性。新方法最大化了中间态的经典库仑能迹，从而压缩了中间态的电子密度。我们表明，CMS-PDFT执行稳健，即使XMS-PDFT失败。
Multiconfiguration pair-density functional theory (MC-PDFT) is a multireference method that can be used to calculate excited states. However, MC-PDFT potential energy surfaces have the wrong topology at conical intersections because the last step of MC-PDFT is not a diagonalization of a model-space Hamiltonian matrix, as done in, for example, multistate second-order perturbation theory (MS-CASPT2). We have previously proposed methods that solve this problem by diagonalizing a model-space effective Hamiltonian matrix, where the diagonal elements are MC-PDFT energies for intermediate states, and the off-diagonal elements are evaluated by wave function theory. One previous method is called variational multistate PDFT (VMS-PDFT), whose intermediate states maximize the trace of the effective Hamiltonian, namely, the sum of the MC-PDFT energies of the model-space states; the VMS-PDFT is very robust but is more computationally expensive than another method, extended multistate PDFT (XMS-PDFT), in which the transformation to intermediate states is accomplished without needing any density functional evaluations. However, although VMS-PDFT was accurate in all cases tested, XMS-PDFT was accurate in only some of them. In the present paper, we propose a new method, called compressed-state multistate PDFT (CMS-PDFT), that is as efficient as XMS-PDFT and as accurate as VMS-PDFT. The new method maximizes the trace of the classical Coulomb energy of the intermediate states such that the electron densities of the intermediate states are compressed. We show that CMS-PDFT performs robustly even where XMS-PDFT fails.