THE CR-2 POTENTIAL-ENERGY CURVE STUDIED WITH MULTICONFIGURATIONAL 2ND-ORDER PERTURBATION-THEORY

The potential energy curve of the Cr-2 ground state has been obtained by multiconfigurational second-order perturbation theory. In this stud y 6-8 singularities appear in the potential curve for bond distances r anging from 1.5 to 2.2 Angstrom. However, these singularities are weak enough to allow the determination of approximate spectroscopic consta nts. By employing a large atomic natural orbital (ANO) basis set of th e size 8s7p6d4f and by including 3s, 3p correlation effects and relati vistic corrections, the following values were obtained (experimental d ata within parentheses): equilibrium bond length r(e)=1.71 Angstrom ( 1.68 Angstrom), harmonic vibrational frequency omega(e)=625 cm(-1) (48 1 cm(-1)) and dissociation energy D-0=1.54 eV (1.44+/-.0.06 eV).