title: Theoretical studies on the bonding and thermodynamic properties of Ge n Si m (m+n=5) clusters: the precursors of germanium/silicon nanomaterials.
abstract: Theoretical studies on the Ge n Si m clusters have been carried out using advanced ab initio approaches. The lowest energy isomers were determined for the clusters with compositions n+m=2-5. All possible isomers arising due to permutations of Ge and Si atoms were investigated. The L-shaped structure for the trimers, tetragonal with diagonal bond for tetramers, and a trigonal bipyramid for pentamers represent the energy optimized ground state geometries. The bonding analyses revealed that the trimers and tetramers are stabilized through multicenter pi bonding. In pentamers, this stabilizing factor is eliminated due to the further cluster growth. The ionization of clusters does not change their geometrical characteristics. The agreement of the calculated ionization and atomization energies with those obtained from the mass spectrometric studies (through estimated appearance potential) validated the reported structures of the clusters. The bonding properties of these species are discussed using their molecular orbital characteristics and analysis of natural bond orbital population data.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland.
authors.forename: Pawel
authors.initials: P
authors.lastname: Wielgus
authors.forename: Szczepan
authors.initials: S
authors.lastname: Roszak
authors.forename: D
authors.initials: D
authors.lastname: Majumdar
authors.forename: Julia
authors.initials: J
authors.lastname: Saloni
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski