Calculation of the Electronic Structure of Lithium Clusters with the SelfConsistent LinearCombination  of  Orbitals Method.
Abstract
The linearcombinationoforbitals method in the local density approximation (LDA) was used to calculate selfconsistently the electronic structure of three lithium clusters, containing 15, 27, and 59 atoms. Subsequently, the 15atom cluster was corrected for selfinteraction selfconsistently and on an orbitalbyorbital basis. In the other two clusters the valence electrons were corrected for selfinteraction in an average way, and only the 27 atom cluster was taken to selfconsistency. The LDA calculation implies the clusters behave very much like spheres of jellium in both the oneelectron energy levels and in the electron density. Jellium electronic shells are easily identifiable in all three clusters, although they are modified somewhat by the aspherical crystalfield splitting of the ionic cores. In the largest cluster the jellium energy levels are clearly seen well above the Fermi level, indicating that a lithium cluster of at least 92 electrons will still have jelliumlike electronic properties. Near spherical symmetry in the valence electron densities of the three clusters implies the nuclei are well screened and the effective potential for these electrons is very much like that experienced by the electrons in the spherical jellium model. Further, Friedel oscillations appearing in the density are quite reminiscent of those seen in self consistent quantummechanical calculations of jellium spheres. Mulliken population analysis of the LDA results are consistent with a convergence to bulk with increasing cluster size, the interior of the largest cluster appearing bulklike in both electron populations and density, even though the Friedel oscillations seem to penetrate to the center of the largest cluster. The selfinteractioncorrection (SIC) results for the clusters confirm that the eigenvalues of this procedure are much more like electron removal energies than those of the LDA. In addition the orbitalbyorbital SIC calculation of the 15atom cluster broadened the energy range of the valence electrons to a value close that of a compatible bulk calculation. A simple technique for estimating the amount of SIC implies that clusters with thousands of atoms would still exhibit significant errors in their LDA eigenvalues.
 Publication:

Ph.D. Thesis
 Pub Date:
 1986
 Bibcode:
 1986PhDT........58R
 Keywords:

 Physics: Condensed Matter