title: Symmetry exploitation in closed-shell coupled-cluster theory with spin-orbit coupling.
abstract: In the present work, we report exploitation of spatial symmetry in calculations of ground state energy and analytic first derivatives of closed-shell molecules based on our previously developed coupled-cluster (CC) approach with spin-orbit coupling. Both time-reversal symmetry and spatial symmetry for D(2h) and its subgroups are exploited in the implementation. The symmetry of a certain spin case for the amplitude, intermediate, or density matrix is determined by the symmetry of the corresponding spin functions and the direct product decomposition method is employed in computations involving these quantities. The reduction in computational effort achieved through the use of spatial symmetry is larger than the order of the molecular single point group. Symmetry exploitation renders application of the CC approaches with spin-orbit coupling to larger closed-shell molecules containing heavy elements with high accuracy.
authors.affiliation: Key Laboratory of Chemical Laser, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
authors.forename: Zheyan
authors.initials: Z
authors.lastname: Tu
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.forename: Jingwei
authors.initials: J
authors.lastname: Guo