Energetics and Kinetics of Ti Clustering on Neutral and Charged C60 Surfaces

Abstract

Abstract: Using ab initio spin density functional theory, we investigate the energetics and kinetics of Ti clustering on both neutral and charged C60 surfaces. We compare the formation energy of twodimensional (2D) and three-dimensional (3D) TiN clusters as a function of cluster size (N���12). We find that there exists a critical cluster size (NC) of NC=5, below which 2D layer structures are preferred to 3D structures. Hole- or B-doping greatly enhance the Ti-fullerene interaction and lead to stronger dispersion of Ti atoms. Even so, for moderate charge doping (less than seven holes) the critical size of Ti atoms on neutral C60 surprisingly remains unchanged or only slightly increases to NC=6 by B-doping. However, we find that the formation of 3D clusters is hindered by a high kinetic barrier related to the 2 process of single Ti atoms climbing up a single Ti layer. This barrier is ~1eV or even 1.47 eV for Bdoped C60 surfaces which is high enough to stabilize larger 2D structures (N���NC) at low temperatures. These findings open a way to produce homogenously Ti-doped fullerenes which are believed to be a very promising material for hydrogen storage.