The prediction of isomers for the phosphorus clusters P₇⁺

In the study of cationic phosphorus cluster produced in direct laser vaporization, it has been observed P₇⁺ shows the highest intensity in the mass spectrum. We acquired twenty-four P₇⁺ isomers with molecular graphics and then carried out optimizations with molecular mechanics, PM3 semi-empirical and ADF density functional calculations. In these isomers, the phosphorus atoms could be in two-fold, three-fold, four-fold or six-fold coordination. P₇⁺ which derived from the most stable P₆ by adding a phosphorus atom against the double bond has the lowest bonding energy. When there is a six-fold atom in the structure, the d orbital is involved in bonding. According to the bonding energies, the models with a planar ring or a six-fold atom are relatively less stable.