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Figure 5 MOOP diagram of the molecular orbitals concentrated on
the La atoms calculated with the EH method for an idealized
La6I18Ge octahedron cluster of La7ϩxI12Ge with r(La-I)/r(La-La)ϭ
0.88. The MOOP is summed over for all the La-La edges in the oc-
tahedron.
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949.
energy of the a2u level descends more rapidly than other
levels. The experimental value of the ratio using the average
distances in the La7ϩxI12Ge structure is near 0.8. Beyond
the ratio of 0.82, a2u is below all other levels except for t2g,
and of all the levels only these two contribute to La-La
bonding. Figure 5 shows the MOOP [38] diagram calcu-
lated with EH method for r(La-I)/r(La-La) equal to 0.88.
Indeed, the lowest t2g and a2u levels are of La-La bonding.
This trend estimated even by the semi-quantitative EH
method helps us to understand the electronic structure of
this type of compounds.
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100, 16092.
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1997, 109, 1892; Angew. Chem. Int. Ed. 1997, 36, 1808.
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Acknowledgement. We thank R. Eger for the sample preparation,
V. Duppel for the EDX measurements and C. Kamella for the draw-
ing of the figures. CZ acknowledges the support by NSF through
grants DMR-9704048 and CHE-9974760, and by the Max-Planck-
Gesellschaft which made his visit at MPI possible.
Supporting Information Available: Further details of the crystal
structures can be obtained from Fachinformationszentrum
Karlsruhe, D-76334 Eggenstein-Leopoldshafen, Germany, or via
e-mail crysdata@fiz-karlsruhe.de free of charge upon quoting the
numbers CSD-414170 for La2I2Ge (1T), CSD-414171 for La2I2Ge
(3R), CSD-414173 for La3Cl2Ge3, CSD-414172 for La3Br2Ge3,
CSD-414174 for La3I3Ge, CSD-414175 for La6I5Ge3 and CSD-
414176 for La7ϩxI12Ge.
[28] U. Schwanitz-Schueller, A. Simon, Z. Naturforsch. 1985, 40b,
710.
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Allg. Chem. 2001, 627, 2151.
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Ed. Engl. 1988, 27, 159.
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1463; Angew. Chem. Int. Ed. Engl. 1992, 31, 1437.
[38] C. Mealli, D. M. Proserpio, J. Chem. Educ. 1990, 67, 399.
References
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308
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