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 (2) Sigma(+) whereas two nearly degenerate states ((1) Sigma(+), (3) Sigma(+)) 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. (C) 1998 Published by Elsevier Science B.V.