title: Beryllium dimer: a bond based on non-dynamical correlation.
abstract: The bond nature in beryllium dimer has been theoretically investigated using high-level ab initio methods. A series of ANO basis sets of increasing quality, going from sp to spdf ghi contractions, has been employed, combined with HF, CAS-SCF, CISD, and MRCI calculations with several different active spaces. The quality of these calculations has been checked by comparing the results with valence Full-CI calculations, performed with the same basis sets. It is shown that two quasi-degenerated partly occupied orbitals play a crucial role to give a qualitatively correct description of the bond. Their nature is similar to that of the edge orbitals that give rise to the quasi-degenerated singlet-triplet states in longer beryllium chains.
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, Université Paul Sabatier , 118, Route de Narbonne, F-31062 Toulouse Cedex, France.
authors.forename: Muammar
authors.initials: M
authors.lastname: El Khatib
authors.forename: Gian Luigi
authors.initials: GL
authors.lastname: Bendazzoli
authors.forename: Stefano
authors.initials: S
authors.lastname: Evangelisti
authors.forename: Wissam
authors.initials: W
authors.lastname: Helal
authors.forename: Thierry
authors.initials: T
authors.lastname: Leininger
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Tenti
authors.forename: Celestino
authors.initials: C
authors.lastname: Angeli
mesh_terms: D001608:Beryllium / Q000737:chemistry*; D019281:Dimerization; D011789:Quantum Theory
chemical_list: D001608:Beryllium