title: On the triplet ground state of tetrahedral X4 clusters (X = Li, Na, K, Cu).
abstract: The lowest electronic state of distorted tetrahedral X(4) clusters (with X = Li, Na, K, Cu) is studied at coupled-cluster level using high-quality atomic basis sets. The ground state is found to have a triplet spin symmetry for this kind of geometry and for all the considered atomic species. The equilibrium geometries correspond to Jahn-Teller-distorted oblate tetrahedra having D(2d) symmetry, and tetrahedric structures are local minima on the potential-energy surfaces for the triplet states. Their energies lie between 0.2 eV (for the K(4) cluster) and 0.9 eV (for Cu(4)) above the absolute minimum of the corresponding systems, which is a spin singlet having a rhombus geometry.
authors.affiliation: Laboratoire de Chimie et Physique Quantiques - IRSAMC, Université de Toulouse et CNRS, 118, Route de Narbonne, F-31062 Toulouse Cedex, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Verdicchio
authors.forename: Stefano
authors.initials: S
authors.lastname: Evangelisti
authors.forename: Thierry
authors.initials: T
authors.lastname: Leininger
authors.forename: Antonio
authors.initials: A
authors.lastname: Monari