Drwal Daria, Pernal Katarzyna, Pastorczak Ewa
Institute of Physics, Lodz University of Technology, ul. Wolczanska 217/221, 93-005 Lodz, Poland.
J Chem Theory Comput. 2024 May 14;20(9):3659-3668. doi: 10.1021/acs.jctc.4c00103. Epub 2024 Apr 26.
We show that accurate oscillator strengths can be obtained from adiabatic connection (AC) approaches based on the extended random phase approximation (ERPA) combined with multireference (complete active space, CAS) wave functions. The oscillator strengths calculated using the perturbation-corrected ERPA transition density matrices, proposed in this work, and the excitation energies calculated with recently introduced AC correlation energy methods, AC0 and AC0D, compete with accuracy in the perturbational CASPT2 approach and require less computational effort. AC0 and AC0D methods scale more favorably with the number of active orbitals than multiconfigurational perturbation approaches like CASPT2 and NEVPT2 thanks to their dependence on reduced density matrices up to the order of 2. Importantly, the newly developed approach for computing correlated transition dipole moments does not entail any additional costs, as all intermediate quantities become available when AC0 energies are being computed. We also test the performance of the recently proposed AC method corrected for the negative-transition contributions to the correlation energy, AC0D, for triplet excitation energies. Similarly, as for the singlet excitations, the correction improves the performance of the AC0 method, particularly for the low-lying excited states.
我们表明，基于扩展随机相位近似（ERPA）并结合多参考（完全活性空间，CAS）波函数的绝热连接（AC）方法，可以获得精确的振子强度。使用本文提出的微扰校正ERPA跃迁密度矩阵计算的振子强度，以及用最近引入的AC相关能方法AC0和AC0D计算的激发能，在微扰CASPT2方法中具有相当的精度，并且所需的计算量更少。由于AC0和AC0D方法依赖于高达二阶的约化密度矩阵，它们与CASPT2和NEVPT2等多构型微扰方法相比，随活性轨道数的缩放更有利。重要的是，新开发的计算相关跃迁偶极矩的方法不会带来任何额外成本，因为在计算AC0能量时所有中间量都已可用。我们还测试了最近提出的针对相关能的负跃迁贡献进行校正的AC方法AC0D对三重态激发能的性能。与单重态激发类似，这种校正提高了AC0方法的性能，特别是对于低激发态。
