直线型C_nP^-(n=1～11)结构的理论研究

Theoretical Studies of Linear C_nP^-(n=1～11) Cluster Ions

以激光溅射方法产生了一系列含一个磷原子的碳原子簇负离子．针对其在实验中呈现的奇偶变化规律进行了量子化学从头算研究．在HF／6－311G*水平上（对单重态为RHF，多重态为ROHF）优化了直线型CnP-（n=1～11）键长和能量，计算了相邻簇离子的能量差与成簇碳原子的平均结合能及从CnP-分别解离C、C2、C3、P、CP、C2P等6种通道所需的能量．计算发现，n为奇数的CnP-单重态（1Σ）最稳定，而，n为偶数的簇离子则以三重态（3Σ）的能量较低．所计算的CnP-各结构参数均表现出奇偶交替的变化规律，n为奇数的CnP-相对稳定．

A series of carbon cluster anions with a phosphorus atom had been produced in theexperiment. Ab initio balculations at the HF/6-311. level were carried out on the cluster ionswith linear configuration. The calculated electronic structure, system energy and fragmenta-tion energies of six dissociation channels exhibit odd/even alternation which agrees very wellwith the experimental observations. According to the calculated results, HOMO of C.P-with odd n is full-filled bonding orbitals, so it is more stable than C.P- with even n, whoseHOMO is also doublet degenerated but it is half-filled non-bonding orbitals. The optimizedbond lengths of the cluster anions show that CusP bond of C.P- with odd n is triplet. Oncontrast, the bond of C.P- with even n is singlet, so it is easier to be broken-