Isomers Prediction for Phosphorus Clusters P8
- 化学化工－已发表论文 
[中文文摘]根据由激光产生的磷原子团簇正离子的质谱图所出现具有规律"奇幻数"的线索，即从开始质谱图的信号强度以8为周期变化，可以推断出从开始稳定的磷原子团簇正离子是以P8为结构单元依次聚合而生成的。使用分子图形软件设计出19种P8的同分异构体，并进行分子力学、PM3半经验量子化学和ADF密度泛函优化．所有的模型中的磷原子均采用二配位和三配位成键．从各异构体成键能量的比较中可得知，笼状结构比平面结构稳定，平面环越大越不稳定，最稳定的P8构型是由12个单键组成的楔状结构．虽然目前还没有P8的实验数据，但在某些单质磷和含磷化合物中含有P8楔状结构单元．楔状结构的P8可认为是由2个很稳定正四面体P4分别断裂4个键后重新生成4个键而产生的．[英文文摘]Analyzing the mass spedrum of phosphorus duster canons produce by direct laser vaporization, after P25+ the intensities of the odd number clusters are stronger than those of the neighboring even number dusters. Relatively high intensities of phosphorus duster cations in the mass spectrum were observed with the formula of n =25 +8k. It indicates that the possible existence of P8 as a polymerization unit to build large phosphorus clusters step by step. According tO the due of the mass spectrum, nineteen P8 isomers were proposed with molecular graphics and then optimized with molecular mechanics,PM3 simi-empirical and ADF density funcitioal calculations.The phosphorus atoms adopted threefold or two fold coordinations in all models.The bonding energies of isomers show that the cape -shape models are more stable than planer one and the models of large planer ring are less stable.The most stable cuneane structure composed by 12 single bonds can be chose as polymerization unit.The bonding energies of some isomers with one double bond are more stable than those of all single bonds.although a neutral P8 cluster has never been obtainde from the experiment ,some structures do contain cuneane P8 units.There is a possibility that two most stable tetrahedral P4units with breaking and making four bonds compose the cuneane structure.The cuneane P8 can form the polymeric structures, i.e.large clusters of phosphorus cation.