Using B3LYP/6-311＋G** method, the initial geometrical structures of boron-carbon clusters C_{2＋nB10－n (n＝0～10) containing double planar pentacoordinate carbon (ppC) were optimized and their vibrational frequencies were calculated. Present results showed that C2＋nB10－n (n＝0～2) clusters are stable, in which the Wiberg bond index (WBI) of ppC—B bonds are between 0.511 and 0.909 and the WBIs of ppC—C are 0.2254 (n＝1) and 0.8586 (n＝2), as well as the WBIs of ppC are 3.778 and 3.879, i.e. the three molecules include double ppCs and ppCs obey octal rule; the C2＋nB10－n (n＝3～6) clusters with the lowest energy contain one ppC, while the lowest energy C2＋nB10－n (n＞6) clusters have no ppC. In addition, only the C2＋nB10－n (n＝0～2) clusters do not include dangling bonds, and the numbers of ( electron in the C2＋nB10－n (n＝0～2) clusters are 6, 7 and 8, respectively. Calculated NICS(0) values indicate that the strong aromaticity mainly locates at the centers of the three-membered rings. The vertical transition energies of C2＋nB10－n (n＝0～2) clusters are 1.91, 0.56 and 3.12 eV.}

Key words: hybrid density functional, planar pentacooridinate carbon (ppC), boron-carbon cluster, aromaticity