Theoretical study of low-lying electronic states of Mn2 using a newly developed relativistic model core potential

We investigated the electronic structure of low-lying electronic states of Mn(2) using a newly developed relativistic model core potential (spdsMCP). Calculations were performed at complete active space self-consistent field (CASSCF) and second-order multiconfiguration quasidegenerate perturbation theory (MCQDPT2) levels. The MCQDPT2 calculations reveal that the 1 Sigma g(+) state is the ground state. Calculated spectroscopic constants are very similar to the results of recent all-electron calculations and experimental values, indicating that the spdsMCP works well for Mn(2), which requires a highly correlated calculation. The wave functions of low-lying states are also analyzed at the CASSCF level. (C) 2008 Elsevier B. V. All rights reserved.