Die Struktur und die Elektronendichte der closo‐Bor‐Cluster B4X4 (X = Br, I), B6X62− (X = H, Cl, Br, I) und B12H122− wurden mittels Pseudopotential‐Hartree‐Fock‐Rechnungen bestimmt. Die Interpretation der Bindungsverhältnisse erfolgte durch Auswertung der Elektronen‐Lokalisierungs‐Funktion (ELF). Die Bereiche hohen ELF‐Wertes besitzen in allen Fällen die Form des zum Bor‐Gerüst dualen Polyders. Sie lassen die 3‐Zentren‐2‐Elektronen‐Bindungen besonders gut erkennen. Der Vergleich zwischen Hartree‐Fock‐ und Extended‐Hückel‐Rechnungen zeigt, daß auch semiempirische Verfahren eine gute Grundlage für eine ELF‐Interpretation sein können.
Semiempirical quantum chemical calculations at the modified-neglect-of-diatomic-overlap self-consistent-field level are performed for differently charged clusters of composition LixC60 with x=0...14. The ground state energies of various isomers are calculated to find the most stable configuration for each cluster stoichiometry. The energies required to remove a Li-atom from these configurations are calculated to determine abundance spectra of distributions of heated LixC60 clusters. These spectra show intensity anomalies at x=6+n (where n=0...+2 is the cluster charge), interpreted to be of electronic origin, and at x=12, interpreted to be of geometric origin. Identical anomalies are observed in experimentally obtained mass spectra of LixC60 clusters.
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