Charge Density Level Structures of Endohedral Metallofullerenes by the MEM/Rietveld Method

Abstract

The bonding nature of metal atoms encapsulated in fullerene cages is important structural information relating to the stability of the metallofullerene endohedral structure. Experimental charge density studies of endohedral metallofullerenes by synchrotron radiation (SR) powder diffraction utilizing the maximum entropy method (MEM) are reviewed. Results of the endohedral metallofullerenes La@C₈₂, Sc@C₈₂, Sc₂@C₈₄, La₂@C₈₀, Sc₃@C₈₂, Sc₂@C₆₆, and Sc₂C₂@C₈₄ are given. The precise MEM charge densities of the metallofullerenes reveal the existence of ionic and/or covalent bonding between metal atoms and the carbon cage, as well as the feature of thermal motion of metal atoms inside the carbon cage. The MEM/Rietveld method, which is the crucial method for data analysis in order to determine the endohedral structure of the fulleride, is also mentioned in some detail.