基于多参考态组态相互作用的自旋－轨道耦合计算方法和程序实现

相对论效应和电子相关是电子结构理论研究的两个基本问题。本项目致力于研究基于精确MRCI和近似MRCI方法如内收缩的MRCI、MRPT2等的自旋轨道耦合(SOC)计算方法和程序，从而在不同层次来考虑SOC效应。首先，通过积分－图形混合驱动和并行化提高现有内收缩MRCI的计算效率，并将MRCI用于电子－原子核广义平均场组态相互作用理论(EN-GMFCI)；其次，基于sf-X2C+so-DKHn自旋分离的哈密顿，发展利用MRCI/icMRCI/MRPT2波函数的态－态相互作用微扰计算SOC效应的程序，图形酉群理论将被用以计算SOC矩阵元；最后，研究在MRCI级别变分包含SOC效应的SOC-MRCI/icMRCI算法和程序。最终形成一个适用于从弱相对论效应的有机分子到强相对论效应5p、6p重元素体系的基于MRCI的自旋轨道耦合计算程序包。

Relativistic effect and electron correlation are two important issues in electronic structure theory. This project will develop a new program package to calculate spin-orbit coupling effect using multi-reference configuration interaction (MRCI) and its approximated methods such as internally contracted MRCI (icMRCI) and multi-reference second order perturbation theory (MRPT2). Firstly, the integral-graphic hybrid driven technique will be employed to develop a highly efficient icMRCI algorithm. A parallel icMRCI program will be developed to improve the computational efficiency further. Also, MRCI will be applied in newly introduced electron-nuclear general mean field configuration interaction (EN-GMFCI) theory. Then, the sf-X2C+so-DKHn Hamiltonian will be used to treat the relativistic effect; the state interaction scheme will be used based on MRCI/icMRCI/MPRT2 to calculate SOC effect in a perturbative manner. The graphic unitary group approach will be employed to calculate SOC matrix element. Finally, a new SOC-MRCI/icMRCI algorithm will be introduced to include SOC effect variationally. A spin-orbit coupling MRCI program package will be developed that can be used not only in weak relativistic system such as organic molecules but also in strong relativistic system such as compounds with heavy 5p and 6p elements.