The cluster Ti_xN_y (x≤3, y≤2) has been calculated by density func-tional theory (B3LYP) with effective core potential basis set. The results show that the spin multiplicity of the system was de-termined by Ti atoms of Ti₂N. The negative charge of N was increased with its number of coordinate in Ti₃N, and every Ti atom afforded about 0.3 charge to the N atom. From the analysis of Ti₂N₂, the more the bonds are formed, the more stable the system is. The bond of N—N was weak-ened with increase of the number of the bonds of Ti—N.

Key words: Ti_xN_y, cluster, quantum chemical calculation