Based on the density functional theoretical (DFT) BPBE and ab initio CCSD(T) calculations, the geometries and stabilities of TiB_n (n＝1—12) clusters have been systematically investigated. For BPBE calculations, the orbitals of B atoms are described by the 6-311+G(d) basis set, and that of Ti atom by CEP-121G basis set. For CCSD(T) calculations, CC-PVTZ basis set is applied for both B and Ti atoms. It is found that the most stable TiB_n clusters can be constructed from the most stable B_n+1 clusters when n≤6, except of TiB₄, by replacing one B atom at the edge of the B_n+1 cluster with one Ti atom. With the increase of n, the TiB_n clusters evolve from planar structure to three-dimensional structure. From TiB₇ to TiB₁₂, the most stable structure has nest-like structure. The calculated second-order difference of energies manifests that the magic numbers of stability are 2, 8 and 10 for the TiB_n clusters in CCSD(T) level, which is different from the result of DFT calculations. Both BPBE and PW91 methods of DFT showed the magic numbers of stability are 3, 7 and 10. This difference implies the importance of electronic correlation in TiB_n clusters. The vertical ionization potentials (VIP) and vertical electronic affinities (VEA) of TiB_n clusters are reported at CCSD(T) level. The TiB_n clusters with closed-shell electronic configuration have smaller VEA and greater VIP, which are more stable in the chemical reactivity view of point.

Key words: TiB_n cluster, stability, ab initio calculation, electronic structure