Abstract: The cluster ions Ti_nP_m⁺generated by laser plasma reaction have been studied by using quantum chemistry ab initio method. The possible geometric structures were examined and optimized. For TiP_m⁺, titanium atom tends to combine with two phosphorus atoms to form planar systems, while TiP₄⁺and TiP₆⁺are more stable than another. There is one growing helix for Ti₂P₄⁺-Ti₂P₈⁺, the number of phosphorus atoms between two titanium atoms grows from four to eight, and these phosphorus take the shapes of tetrahedron, pentagon, octahedron or cube, etc. It is found that Ti₃P_m⁺and Ti₄P_m⁺in many titanium phosphide are more stable.

Key words: Titanium phosphorus compound, Cluster ions, Plasma reaction, Ab initio