The charge density study of fullerenen compounds by the MEM

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This research project had been carried out to reveal the experimental charge densities of fullerene compounds using the Maximum Entropy Method(MEM) combined with Rietveld analysis, which is called as MEM/Rietveld analysis. Consequently, the work was achieved successfully and revealed the structures in charge density level for the novel endohedral metallofullerenes. Among them, the success of the structural analysis of IPR(Isolated Pentagon Rule)-violated metallofullerene, Sc_2@C_<66>, was one of the greatest results in this project. This has been published in Nature (408(2000)426)and reported in some news papers. The result gave the breakthrough in the criteria for the stable geometry of the metallofullerene cage structure, that is, the IPR is not necessarily a test for the stable geometry of endohedral metallofullerenes In addition, it was found that the charge-transfer interaction between the Sc_2 dimer and the fused pentagons significantly decreases the strain energies caused by the pair of fused pentagons and thus stabilizes the fullerene cage. Another important result is the structure determination of the Sc_2C_2 cluster encapsulated in C_<84> for Sc_2C_2@C_<84>. This is the first report of the structure of fullerene encapsulating Sc-carbide molecule and has an impact on the research of the novel endo-fullerene. The result was published in Angew. Chem. Int'l. Ed. 40 (2001) 397 as the very important paper and the charge density of Sc_2C_2@C_<84> was appeared as the cover picture of Angew. Chem. Int'l. Ed. 40 No.2(2001).No doubt the experimental structural information we provided through this project gave one of the greatest forward push to a research of fullerene compounds.