The cluster ions TinPm+ generated by laser plasma reaction have been studie
d by using quantum chemistry ab initio method. The possible geometric struc
tures were examined and optimized. For TiPm+, titanium atom tends to combin
e with two phosphorus atoms to form planar systems, while TiP4+ and TiP6+ a
re more stable than another. There is one growing helix for Ti2P4+-Ti2P8+,
the number of phosphorus atoms between two titanium atoms grows from four t
o eight, and these phosphorus take the shapes of tetrahedron, pentagon, oct
ahedron or cube, etc. It is found that Ti3Pm+ and Ti4Pm+ in many titanium p
hosphide are more stable.