摘要
在激光产生的磷原子团簇正离子的质谱图中 ,P7+ 具有最强的谱峰 .使用分子图形软件设计出 2 4种 P7+ 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 .在磷原子团簇正离子模型中 ,磷原子采用二、三、四或六配位方式成键 .从各异构体成键能量的比较中可得知 ,最稳定的 P7+ 构型是在最稳定的 P6的双键位置增加 1个磷原子所生成的结构 .在磷原子六配位的结构中 ,d轨道参与成键 .具有平面或六配位原子的 P7+ 结构是不稳定的结构 .
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,implying that P7+ is the most abundant amidst cationic clusters.We acquired twenty- four P7+isomers,their corresponding symmetry beng C2 v,Cs,C3v,D6h,D3d,D3h,D2 d and D2 h,with molecular graphics0 and then carried out optimizations with molecular mechanics,PM3semi- empirical and ADF density functional calculations.Six- fold coordination occurs only in some special configurations.In these isomers,the phosphorus atoms could be in two- fold,three- fold, four- fold or six- fold coordination.It is necessary to consider enough isomers in order to confirm which is the most stable.P7+can be formed by adding a phosphorus atom and a positive charge to a P6 isomer.P7+which derived from the most stable P6 by adding a phosphorus atom against the double bond has the lowest bonding energy.The middle atom in the sandwich structures and the center atom of planar structure trend to be six- fold. According to atomic populations of the three- fold and six- fold atom,the d orbital of six- fold atoms is obviously involved in bonding.Compared to the other structures,the models with six- fold atom are energetically unfavorable and indeed structurally unstable.From the bonding energies,the models with a planar ring or a six- fold atom are relatively less stable. The results can be used as guiding factors for future theoretical investigation;they are also helpful information to the understanding of novel cluster materials.
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
2000年第3期341-347,共7页
Journal of Xiamen University：Natural Science
基金
国家自然科学基金!重大课题
国家自然科学基金资助项目!(2 9573117)
关键词
磷原子团簇
同分异构体
分子图形
分子力学
配位
phosphorus clusters
isomers
P7+
molecular graphics
molecular mechanics
density functional
