Calculating Spin-orbit Coupling with Q-Chem

  • Different spin states mix up through spin-orbit coupling (SOC), thus it is essential to determine SOC to describe spin-forbidden processes, such as phosphorescence, intersystem crossing and spin-crossover, as well as magnetic properties;

  • Q-Chem can calculate SOC at different levels of non-relativistic theory: a) CIS(TDA)/RPA(TDDFT); b) restricted active space configuration interaction (RASCI); c) equation-of-motion coupled cluster (EOM-CC);

  • The one-electron SOC can be evaluated using the one-electron Breit-Pauli operator or scaled nuclear charges;

  • The full SOC can be evaluated using a mean-field treatment of the 2-electron part of the Breit-Pauli operator;

  • All methods for SOC calculations can be combined with spin-flip excitations;

  • Tools for visualizing SOC natural transition orbitals are available.