Impurity Doping of a Simple Metal Cluster: An Ab Initio Study of Li9F

Abstract

The ground-state properties of the doped alkali-metal cluster, LigF, have been investigated using extended basis Hartree-Fock calculations. Six isomers were found. The excited states of the isomers were modeled via configuration-interaction singles (CIS). Differences between the optical response of the isomers with an external fluorine and with an internal fluorine were found. Comparisons are also made between the CIS results for the isomers of LigF and the homogeneous clusters, Lis and Lig+. The ground-state studies show that the metallic Lis core is resistant to substantial modification; the added LiF modifies the geometry and the symmetry in all six isomers, but the frontier molecular orbital structure is only slightly changed from the parent Lis cluster.All six isomers found are substantially noncentrosymmetric. The reduced symmetry permits optical absorption at many more frequencies than can be seen in the more highly symmetric Lis or Lis+ parents, but the overall spectral pattern is very similar.

Bimetallic Clusters

“…The collective plasmon is redshifted and broadened with respect to Na 8 . Quantum chemical calculations for Li 9 F have revealed where the F atom resides [42]. The ground state has low symmetry (C s ), and the F atom resides in an external position and has three close neighbors.…”

Some recent applications of ab initio electronic structure methods to metal, semimetal, and molecular clusters

“…Dahlseid et al [136] have recently studied LigF in HF calculations, finding 6 isomers. The most stable structure appears to resemble a core of Li 8 with lithium fluoride attached.…”

Continuous Symmetry Measures of Density Maps

“…The focus of our report is on the computational tool, and we have selected to demonstrate it on a problem of practical relevance, namely, the structure and symmetry of metal clusters . In the framework of this Festschrift, we recall Ratner’s studies on alkali-metal clusters, where, interestingly, he uses the terms “substantially non-centrosymmetric”, “reduced symmetry”, and “more highly symmetric”all of which can now be replaced by the language and scale of “degree of symmetry”, as demonstrated in sections −; first, however, we describe the copper clusters we use as a model.…”