A theoretical study of the potential energy curves and spectroscopic constants of TaC and TaC+

Potential energy curves for the various low-lying electronic states of TaC and TaC+ have been studied using the complete active space multiconfiguration self-consistent field method (CASMCSCF) followed by first-order and restricted second-order configuration (FOCI, SOCI) interaction calculations. The effect of spin–orbit interactions has been studied using the relativistic configuration interaction method. The ground state of TaC has been found to be 2Σ+ whereas two nearly degenerate states (1Σ+, 3Σ+) are found as candidates for the ground state of TaC+. Inclusion of spin–orbit effect yields a state 1/2 as the ground state of TaC, while in case of TaC+ 1 and 0− states are very close in energy.