Vibrational Frequencies Of Clusters Research Articles

ChemInform Abstract: Ab initio Study of Structure and Bonding of Strontium Clusters.

Strontium clusters with 2 to 13 atoms have been studied by means of high level quantum chemical ab initio calculations using a scalar-relativistic energy-consistent large-core pseudopotential, a corresponding corepolarization potential, large valence basis sets including up to g functions as well as coupled-cluster and configuration interaction correlation treatments. Equilibrium structures, cohesive energies, vertical as well as adiabatic ionization potentials and electron affinities are reported. Vibrational frequencies for clusters with up to 5 atoms also have been determined. To demonstrate graphically the transition from van der Waals to covalent interactions for increasing cluster size and to comment on the contributions of sp and sd hybridization to chemical bonding, the electron localization function (ELF) has been calculated from the Hartree-Fock wave functions for the equilibrium structures determined in correlated calculations. Strontium clusters behave rather differently from clusters of the group 12 elements as well as ytterbium, i.e., they exhibit significantly larger cohesive energies than ytterbium clusters due to more pronounced covalent contributions to bonding, and much lower ionization potentials and smaller band gaps. These differences can be mainly attributed to the considerable sp as well as sd hybridization in strontium clusters, while only either the former or the latter is important for group 12 and ytterbium clusters, respectively.

Ab Initio Study of Structure and Bonding of Strontium Clusters

Strontium clusters with 2 to 13 atoms have been studied by means of high level quantum chemical ab initio calculations using a scalar-relativistic energy-consistent large-core pseudopotential, a corresponding core-polarization potential, large valence basis sets including up to g functions as well as coupled-cluster and configuration interaction correlation treatments. Equilibrium structures, cohesive energies, vertical as well as adiabatic ionization potentials and electron affinities are reported. Vibrational frequencies for clusters with up to 5 atoms also have been determined. To demonstrate graphically the transition from van der Waals to covalent interactions for increasing cluster size and to comment on the contributions of sp and sd hybridization to chemical bonding, the electron localization function (ELF) has been calculated from the Hartree−Fock wave functions for the equilibrium structures determined in correlated calculations. Strontium clusters behave rather differently from clusters of the group 12 elements as well as ytterbium, i.e., they exhibit significantly larger cohesive energies than ytterbium clusters due to more pronounced covalent contributions to bonding, and much lower ionization potentials and smaller band gaps. These differences can be mainly attributed to the considerable sp as well as sd hybridization in strontium clusters, while only either the former or the latter is important for group 12 and ytterbium clusters, respectively.

On the Importance of 5d Orbitals for Covalent Bonding in Ytterbium Clusters

Ytterbium clusters with three to seven atoms have been studied by means of high-level quantum chemical ab initio calculations using energy-consistent relativistic large- and medium-core pseudopotentials, core-polarization potentials, a coupled-cluster electron correlation treatment, and large valence basis sets up to g functions. We have determined equilibrium structures, cohesive energies, vertical ionization potentials, and electron affinities, as well as vibrational frequencies for clusters with up to six atoms. To demonstrate graphically the transition from van der Waals to covalent interactions with increasing cluster size, the electron localization function (ELF) has been calculated from the Hartree−Fock wave functions for the equilibrium structures obtained from the correlated calculations. Yb clusters behave rather differently from those of group 12, though both have similar equilibrium structures, i.e., they exhibit significantly larger cohesive energies and more pronounced covalent contributions...