Electronic states and geometries of small Be clusters

Abstract

Ab initio calculations were carried out on all regular geometric configurations of beryllium clusters containing three through seven atoms. Restricted Hartree-Fock, unrestricted Hartree-Fock, and fourth-order Mlhller-Plesset perturbation theory (MP4) using a 6-31G basis set were used to study singlet, triplet, and quintet spin states of each cluster. The septet state of the most stable nuclear configuration of Be 7 was also examined using unrestricted Hartree-Fock theory. In addition, Be 4 was examined as a prototype for larger clusters, for which accurate calculations may not be computationally feasible. The most stable symmetric nuclear configuration and electronic state of Be 4 was determined at increasingly improved levels of approximation. Hartree-Fock, configuration interaction, and Mlhller-Plesset perturbation theory calculations were carried out using 6-31 G, 6-311 G, 6-31 G*, and 6-311 G* basis sets. Binding energies for the most stable configuration of each cluster were improved by MP4 calculations in a 6-31G* basis set. Be-Be internuclear separations for the lowest electronic state of each cluster range from 1.9 to 2.5 A. MP4 calculations predict singlet ground states for Be 3 , Be 4 , and Be s , whereas Be6 and Be 7 are found to have quintet ground states. Trigonal Bipyramid Pentagon Linear FIG. 1. Five-atom clusters.

Structure and Stability of Be5, Be5+, and Be5-Clusters

“…Marino and Ermler 20 reported the MP4/6-31G bond distances to be 2.040 and 2.116 Å, respectively. Whiteside et al 21 reported the SCF bond distances are 2.028 and 2.099 Å. Lee et al 15 determined that the CCSD/7s3p2d optimized bond distances are both 2.079 Å.…”

The Beryllium tetramer: Profiling an elusive molecule

“…27 Study of Be 4 was originally motivated by the prediction of ab initio computations that it would form the smallest significantly bound beryllium cluster. 21,27,36,55,56,58 The dissociation energy also shows a large basis set dependence. 21,27,36,55,56,58 The dissociation energy also shows a large basis set dependence.…”

Subregional organization of preoptic area /anterior hypothalamic projections to arousal-related monoaminergic cell groups

“…The nature of the evolution of crystal properties, from packing of atoms, has been a topic interest for many years 6–17. The investigation of changes in various structural and electronic properties of these systems with crystal growth and the number of atoms necessary to reproduce a complete tri‐periodic system have been the subject of many studies.…”