Correlation in first-row transition metal atoms using generalized Mo/ller–Plesset perturbation theory

Abstract

Correlation effects in the lowest lying states arising from the 4s23dn, 4s3dn+1, and 3dn+2 configurations of the first-row transition metal atoms, Ti, Cr, Fe, and Ni are studied using a generalized Mo/ller–Plesset perturbation theory applicable to multiconfigurational reference wave functions. Reference wave functions including configurations describing the dominant 4s2 angular and 3d radial correlation effects are found to be essential for a perturbative treatment of these atoms. Generalized Mo/ller–Plesset theory applied to such multiconfigurational reference wave functions gives relative energies comparable to corresponding multireference configuration interaction (CI) calculations at a lower computational cost.