From Carbides to Co 5 and Co 13 Metallofullerenes: First-Principles Study and Design

Trigonal-bipyramidal Co5 and icosahedral Co13 magnetic clusters were investigated in various organic environments by the first principle calculations based on the density functional theory (DFT). Adjacent carbon atoms decreased the total spin magnetic moment of the metallic clusters, such that Co5C5 and C13C12 carbides demonstrated 23.1 and 22.6 %, as well as Co5@C60 and Co13@C80 endohedral matallofullerenes showed 80.5 and 87.1 % of magnetic activities of pure cobalt clusters, respectively. As a result of increasing the number of carbon atoms on the surface, reduction of magnetism and saturation of suppression of magnetic activity was clearly shown in the case of Co13Cn carbide particles. An asymmetric impact of carbon atoms on magnetism of cobalt clusters was revealed and the screen effect depending on the size of fullerenes was described. The endohedral fullerene Co5@C80 demonstrated improved characteristics, such as 90.6 % remaining magnetic activity of pure Co5 cluster, highest magnetic moment at 2.39 µB/Co-atom, and a size of 8.5 A. Since a variety of materials can be nanosized, the scope and limitations of an ab initio approach for scaling design is discussed.