title: Accurate nonrelativistic ground-state energies of 3d transition metal atoms.
abstract: We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |Ec|.
authors.affiliation: Lab. Chimie et Physique Quantiques, CNRS-Université de Toulouse, Toulouse, France.
authors.forename: A
authors.initials: A
authors.lastname: Scemama
authors.affiliation: Lab. Chimie et Physique Quantiques, CNRS-Université de Toulouse, Toulouse, France.
authors.forename: T
authors.initials: T
authors.lastname: Applencourt
authors.affiliation: Lab. Chimie et Physique Quantiques, CNRS-Université de Toulouse, Toulouse, France.
authors.forename: E
authors.initials: E
authors.lastname: Giner
authors.affiliation: Lab. Chimie et Physique Quantiques, CNRS-Université de Toulouse, Toulouse, France.
authors.forename: M
authors.initials: M
authors.lastname: Caffarel