title: Quantum Monte Carlo study of the ground state and low-lying excited states of the scandium dimer.
abstract: A large set of electronic states of scandium dimer has been calculated using high-level theoretical methods such as quantum diffusion Monte Carlo (DMC), complete active space perturbation theory as implemented in GAMESS-US, coupled-cluster singles, doubles, and triples, and density functional theory (DFT). The 3 Sigma u and 5 Sigma u states are calculated to be close in energy in all cases, but whereas DFT predicts the 5 Sigma u state to be the ground state by 0.08 eV, DMC and CASPT2 calculations predict the 3 Sigma u to be more stable by 0.17 and 0.16 eV, respectively. The experimental data available are in agreement with the calculated frequencies and dissociation energies of both states, and therefore we conclude that the correct ground state of scandium dimer is the 3 Sigma u state, which breaks with the assumption of a 5 Sigma u ground state for scandium dimer, believed throughout the past decades.
authors.affiliation: Kimika Fakultatea, Euskal Herriko Unibertsitatea, PK 1072, 20080 Donostia, Euskadi, Spain. jonmattin.matxain@ehu.es
authors.forename: Jon M
authors.initials: JM
authors.lastname: Matxain
authors.forename: Elixabete
authors.initials: E
authors.lastname: Rezabal
authors.forename: Xabier
authors.initials: X
authors.lastname: Lopez
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Ugalde
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi