Vergleich der Elektronendichteverteilungen des Hydrido-Interstitialkomplexes HNb6I11 und des Interstitalhydrids HNb Ein Beitrag zur Cluster-bulk-Analogie

Comparison of Electron Density Distributions in the Hydrido-interstitial Complex HNb₆I₁₁ and in the Interstital Hydride HNb: A Contribution to Cluster-Bulk-Analogy The SW? Xα? SCF method has been used to compare changes of the electronic distributions in Nb₆I₁₁ and in Nb-metal caused by hydrogen at the octahedrally coordinated interstitial sites. Density maps of clusters Nb₆, Nb₆, Nb₆I₈³⁺, and HNb₆I₈³⁺ show: 1. The influence of the iodine ligands on the electronic distribution at the interstitial site is slight. 2. The spherically symmetric electron density of hydrogen at the interstitial sites is only deformed by the bonds to the neighbouring niobium atoms in both cases. Difference electron density maps illustrate that the interstitial hydrogen is weakly polarized in HNb₆I₁₁ as well as in HNb.     

Analytical calculation of binding energies of highly symmetrical particles

Analytical formulae of binding energies per atom are derived for icosahedral, cuboctahedral and face-centered cubic particles A_N by means of summation of pair potentials. Asymptotical relations for larger particles E/N = V (A – BN^−1/3) as well as the topological model of clusters are discussed.     

Particle size effects of clusters and crystallites

Size effects of pair distance, cohesive energy, surface stress, and compressibility have been calculated for shell-like structurated particles Y _N ofn complete shells (units Y: rare gases, molecules, ion pairs). The influence of surface definition on size effects has been discussed.