B_2C_n^+(n=1～9)团簇的结构及其稳定性

Structure and Stability of B_2C_n^+(n=1～9) Clusters

采用密度泛函理论(DFT)的B3LYP泛函,在6-311G*水平上对B2Cn+(n=1～9)团簇的几何构型和电子结构进行了优化和振动频率计算.结果表明,在B2Cn+(n=1～9)团簇的基态构型中,B2C2+、B2C3+为具有D∞h对称性的线形结构,B2C7+为具有Cs对称性的立体环状结构,其余均为平面构型;其成键顺序为C—C成键优于B—C成键,B—C成键优于B—B成键.进一步得到了B2Cn+(n=1～9)团簇的总能量(ET)、零点能(EZ)、摩尔热容(Cp)、标准熵(S0)以及原子化能(ΔEn+).其结果显示,随着n的递增,ET、EZ、Cp、S0和ΔEn+数值均呈现增大趋势,其中EZ数值呈现近似等梯度的增加趋势.通过对B2Cn+(n=1～9)团簇基态结构的垂直电子亲合势的研究发现,n为奇数的B2Cn+团簇比n为偶数的稳定.

Using the B3LYP（Becke-3-parameter-Lee-Yang-Parr） method of density functional theory（DFT）, the geometries and electronic structures of boron-doped carbon clusters of the type B2CN^＋ （n=1-9） have been optimized at 6- 311G^＊ basis set level. Frequency calculations at the same level of theory were performed to characterize the nature of the optimized structures. The calculation results show that most of the ground state structures for B2CN^＋（n=1-9） clusters are planer except that for B2C2^＋and B2C3^＋ are linear structure with D∞h symmetry and three-dimensional monocycle with C, symmetry for B2C7^＋. The preference order for the bonding in the ground state of B2Cn^＋ （n=1-9） clusters is C-C 〉 B-C 〉 B-B. In addition, the total energy（ET）, zero point energy（EZ）, molar heat capacity（CP）, standard entropy（S^0） and atomization energy （AEn^＋） of B2Cn^＋ （n=1-9） clusters are also obtained. The ET, EZ, CP and S^0 values tend to increase with increasing n, in which the increasing zero point energy（Ez） has an approximately constant gradient. The vertical electron affinities of the most stable B2Cn^＋ （n=1-9） clhsters indicate that B2Cn^＋ with odd n is more stable than that with even n.