Sajeev Y, Thodika Mushir, Matsika Spiridoula
Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai 400085, India.
Department of Chemistry, Temple University, 1901 N 13th Street, Philadelphia, Pennsylvania 19122, United States.
J Chem Theory Comput. 2022 May 10;18(5):2863-2874. doi: 10.1021/acs.jctc.1c01096. Epub 2022 Apr 11.
A simple, practical quantum chemical procedure is presented for computing the energy position and the decay width of autoionization resonances. It combines the -stabilized resonance wave function obtained using the real-valued continuum-remover (CR) potential [Y. Sajeev , , 105-112] and the Feshbach projection operator (FPO) partitioning technique. Unlike the conventional FPO partitioning of the total wave function into its resonant and background components, an explicit partitioning of the total wave function into its interaction region and noninteraction region components is obtained with the help of real-valued continuum-remover potential. The molecular system is initially confined inside a CR potential which removes the electronic continuum of the molecular system in which its resonance state is embedded and, thus, unravels the component of the resonance wave function as a bound, localized eigenstate of the confined system. The eigenfunctions of the molecular Hamiltonian represented in the constitute a complementary, orthogonal . A unique partition is obtained when the level-shift of the function due to its coupling with the is zero, and the resonance width is computed using these unique partitioned spaces. This new procedure, which we refer to as CR-FPO formalism, is formally very simple and straightforward to implement, yet its applications to the resonance state of a model Hamiltonian and to the doubly excited resonance states of atomic and molecular systems at the full-CI level are very accurate as compared to the alternative, very precise methods. In addition, the CR-FPO formalism is implemented in the multireference configuration interaction (MRCI) method, and uses it for calculating the energy position and the autionization decay width of Π shape resonance in .
提出了一种简单实用的量子化学程序，用于计算自电离共振的能量位置和衰变宽度。它结合了使用实值连续体去除器（CR）势获得的稳定共振波函数[Y. Sajeev ， ，105 - 112]和费什巴赫投影算符（FPO）划分技术。与将总波函数常规FPO划分为其共振和背景分量不同，借助实值连续体去除器势可将总波函数明确划分为其相互作用区域和非相互作用区域分量。分子系统最初被限制在一个CR势内，该势去除了其共振态所嵌入的分子系统的电子连续体，从而将共振波函数的分量揭示为受限系统的一个束缚、局域本征态。在中表示的分子哈密顿量的本征函数构成一个互补的正交。当函数由于与耦合引起的能级移动为零时，可得到一个独特的划分，并使用这些独特的划分空间计算共振宽度。我们将这个新程序称为CR - FPO形式主义，它在形式上非常简单且易于实现，然而与其他非常精确的方法相比，其在全CI水平下对模型哈密顿量的共振态以及原子和分子系统双激发共振态的应用非常准确。此外，CR - FPO形式主义在多参考组态相互作用（MRCI）方法中实现，并用于计算中Π形共振的能量位置和自电离衰变宽度。
