Guo Yang, Zhang Ning, Liu Wenjian
Qingdao Institute for Theoretical and Computational Sciences, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao, Shandong 266237, China.
Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
J Chem Theory Comput. 2023 Oct 10;19(19):6668-6685. doi: 10.1021/acs.jctc.3c00789. Epub 2023 Sep 20.
It has recently been shown that the SOiCI approach [Zhang, N.; 2022, 34, 224007], in conjunction with the spin-separated exact two-component relativistic Hamiltonian, can provide very accurate fine structures of systems containing heavy elements by treating electron correlation and spin-orbit coupling (SOC) on an equal footing. Nonetheless, orbital relaxations/polarizations induced by SOC are not yet fully accounted for due to the use of scalar relativistic orbitals. This issue can be resolved by further optimizing the still real-valued orbitals self-consistently in the presence of SOC, as done in the spin-orbit coupled CASSCF approach [Ganyushin, D.; 2013, 138, 104113] but with the iCISCF algorithm [Guo, Y.; 2021, 17, 7545-7561] for large active spaces. The resulting SOiCISCF employs both double group and time reversal symmetries for computational efficiency and the assignment of target states. The fine structures of p-block elements are taken as showcases to reveal the efficacy of SOiCISCF.
最近的研究表明，SOiCI方法[Zhang, N.; 2022, 34, 224007]与自旋分离的精确二分量相对论哈密顿量相结合，通过在同等基础上处理电子关联和自旋轨道耦合（SOC），可以为包含重元素的系统提供非常精确的精细结构。尽管如此，由于使用了标量相对论轨道，SOC引起的轨道弛豫/极化尚未得到充分考虑。这个问题可以通过在SOC存在的情况下自洽地进一步优化仍然是实值的轨道来解决，就像在自旋轨道耦合CASSCF方法[Ganyushin, D.; 2013, 138, 104113]中那样，但对于大活性空间使用iCISCF算法[Guo, Y.; 2021, 17, 7545 - 7561]。由此产生的SOiCISCF利用双群和时间反演对称性来提高计算效率和目标态的分配。以p区元素的精细结构为例来展示SOiCISCF的有效性。
