A new implementation of spin-orbit couplings for EOM-CC and their analysis
Pavel Pokhilko1, Evgeny Epifanovsky2, Anna Krylov1
1. Department of Chemistry, University of Southern California, Los Angeles, CA, United States.
2. Q-Chem, Inc., Pleasanton, CA, United States.
Spin-orbit mean field (SOMF) has been implemented through a producer-consumer model in Q-Chem using libqints integral library. The implementation avoids unnecessary storage of two-electron spinorbit integrals. The theory was reformulated using Wigner-Eckart theorem, to enable generation of transition densities corresponding to all multiplet components from the transition density computed for just one pair of states with chosen spin projections. This allows one to compute all components of spinorbit matrix elements needed for spin-orbit coupling constants (SOCC) and splittings. The solution to the phase problem is also presented. This general approach was implemented for equation-of-motion coupled-cluster wave functions. SOMF artifacts for open-shell references will be discussed. The new density matrix has been analyzed in terms of natural transition orbitals (NTO) and spin-orbit integrals between them using libwfa library.