Self-consistent electronic structure of lithium clusters

The electronic structure of Li clusters with 15, 27, and 59 atoms has been calculated self-consistently with use of the linear combination of atomic orbitals method. The results suggest that the conduction electrons in these clusters behave much like electrons in the spherical jellium-background model in that a similar shell-like structure is seen, albeit split by the crystal field. Friedel oscillations that appear in the conduction electron density are also much like those of jellium-sphere calculations. The crystal field removes the high degeneracy of the spherical symmetry, distributing the energy levels over the conduction band without destroying the shell-like structure. For clusters in the size range investigated, large energy gaps between shells should strongly influence cluster stability. Stability may also depend on crystal-field splitting to a lesser degree. In larger clusters the energy gaps between shells will become comparable to the crystal-field splitting and the shell-like structure will disappear. Mulliken population analysis and conduction-band widths indicate a trend towards bulk with increasing cluster size, although the electron density in the center of the largest cluster may not be entirely bulklike because of the penetration of Friedel oscillations. 25 ref.--AA