Relativistic Density Functional Theory Investigations Of CY_n And YC_n(n=1-14) Clusters

The geometries, stabilities, and electromagnetic characteristics of CY_n and YC_n(n=1-14)clusters have been systematically investigated by using relativistic density functional theory with generalized gradient approximation. The results:The growth process of CY_n(n=1-14) clusters can be divided into three phases. First, the C atom is adsorbed on the surface of the Yn cluster when n<6. For the cluster with n=6, the C atom goes into the center of a tetragonal bipyramid and the C@Y6 cluster is formed. Over the range from n=7 to 14, Y atoms are successively capped onto the C@Y6 sub-cluster. Due to the C doping, the stability is enhanced and the magnetic moments is reduced compared to the corresponding pure yttrium clusters. In particular, substitutional doping with a carbon atom whether at the surface or subsurface can make some clusters from a open electronic shell to a closed electron shell.The growth process of YC_n(n=1-14) could also be divided into three phases: n<7,the lowest-energy clusters are all fan isomers; 7≤n≤12,the clusters change from fan structure to ring structure,then finally turn to be a 3D carbon-ring structure with the yttrium atom on the top, which is a transitional processes; n>12, the clusters convert back into a planar construction, in which the Y atom move from the vertex position into the centre of the carbon-ring. When taking about average binding energy, the second-order difference, the embedding energy, and the incremental binding energy, we get to know that the CY4 and CY6 cluster are the most stable ones. Mulliken population analysis reveals that the charges always move from Y atoms to C atom among all different sized clusters. The total magnetic moments are all 1μB, and most of them should be attributed to the yttrium atom.