Two-Component Spin-Orbit Coupled-Cluster Methods using MeanField Spin-OrbitIntegrals
Junzi Liu, Ayush Asthana, and Lan Cheng
Department of Chemistry, Johns Hopkins University, Baltimore, MD, USA
A novel implementation of two-component spin-orbit (SO) coupled-cluster singles and doubles (CCSD) method, the CCSD augmented with the non-iterative inclusion of triple excitations [CCSD(T)] method, and the equation-of-motion CCSD (EOM- CCSD) methods using mean-field SO integrals [1] is presented. The new implementation of SO-CC methods features atomic-orbital based algorithms for the particle-particle ladder terms in the CCSD and EOM-CCSD equations, which not only remove the computational bottleneck associated with the large molecular-orbital integral file, but also reduce the floating operation counts for the particle-particle ladder terms by around a factor of four by taking advantage of the spin-free nature of the instantaneous electron-electron Coulomb interaction. Benchmark SO-CC calculations of the ground- and excited-state energies and properties using the exact two-component Hamiltonian [2-4] with atomic mean-field SO integrals [5, 6] are presented to demonstrate the accuracy and applicability of the SO-CC methods in applications to heavy-element containing compounds.
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