| Abstrakt: |
It has been shown, using a "model-potential" analysis, that -C[sub n]/R[sup n] dispersive terms can be an important part of the physical bonding in M[sup +]/Rg complexes (M[sup +]=atomic metal ion, Rg=rare gas atom) for M[sup +] ions with large, polarizable outer-shell electron clouds. The model potential equation consists of all attractive terms (accurately calculated or estimated) out to 1/R[sup 8], as well as an Ae[sup -bR] repulsive term. From known D[sub e], R[sub e], and ω[sub e] values, and the first and second derivatives of the model potential, the repulsive constants A and b as well as the effective charge Z of M[sup +] in a particular M[sup +]·Rg electronic state, can be determined. For the typical M[sup +]·Rg states considered here, Z=1.02±0.07, indicating that no extra "chemical" effects are necessary to explain M[sup +]/Rg bonding. Furthermore, the trends in the derived Ae[sup -bR] repulsive curves make good qualitative sense. A term-by-term analysis for M[sup +]·Rg states where the M[sup +] ion is small and unpolarizable [such as Na[sup +](2p[sup 6])·Rg] shows that -C[sub n]/R[sup n] terms contribute only a few percent to the bond strengths, while for M[sup +]·Rg states where M[sup +] is large and polarizable [for example, Mg[sup +](3s)·Rg], the -C[sub n]R[sup n] terms can contribute on the order of 40%-50% to the bond strengths, thus rationalizing semiquantitatively several heretofore puzzling D[sub e], R[sub e], ω[sub e] comparative values. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
