This paper employed density functional theory (DFT) B3LYP method to optimize the structures of 14-vertex closo-carborane clusters at 6-31G(d) level and the stabilities, charge distributions and energy levels of frontal molecular orbital were analyzed. The results indicated that the stable structures of nine C₂B₁₂H₁₄ isomers were obtained and their molecular backbone structures remained that of B₁₄H₁₄^2－. Besides the stability of 1,14-C₂B₁₂H₁₄ with two C atoms substituted for B atoms in axial position, the stabilities increase with the increasing of distances between the two C atoms. The substitution of C atoms for B atoms in the higher coordination number position decreases the stability. The negative charge of each isomer is distributed mainly among the C atoms and the rest is among the axial B atoms, and the positions of C atoms and the axial B atoms may become the active regions of the nucleophilic reaction. The trend of HOMO energy levels of the isomers is coincided with their stabilities, and the isomer having lower HOMO energy level is more stable.

Key words: C₂B₁₂H₁₄ isomer, stability, frontal molecule orbital, DFT