The prediction of isomers for phosphorus clusters P-8 and P-9(+)

In the study of cationic phosphorus clusters produced in direct laser vapor ization, it has been realized that P-8 and P-9(+) are entities to be consid ered in mass spectrum interpretation. We acquired 20 P-8 and 19 P-9(+) isom ers with molecular graphics and then carried out optimizations with molecul ar mechanics, PM3 semi-empirical and ADF density functional calculations. I n these isomers, the phosphorus atoms adopt twofold, threefold or fourfold coordination. According to the bonding energies, the cage-shape models are more stable than the planar ones, and the models with a large planar ring a re the least stable. The most stable cuneane P-8 structure with 12 single b onds was adopted as the basic unit for polymerization. By adding a phosphor us atom to the bottom right side of cuneane and assuming a positive charge for optimization, we derived P-9(+) isomers and identified the one with the lowest bonding energy, We detected that the P-9(+) isomers with double bon ds are less stable and the distortion of P-9(+) somers with high symmetry w ould result in lower bonding energies. (C) 2000 Elsevier Science B.V. All r ights reserved.