Abstract: There is considerable interest in metal-carbon clusters because of the possible applications of metal-carbon cluster to catalytic and new electronic materials,pollution control,chemical tracers,superconductive materials and in site-specific protein chemistry.In recent years,studies have especially focused on transition-metal carbon clusters.In this paper,quantum chemical ab initio method is used to study the geometric and electronic structures of the Mo₂C₈ cluster.In trying to determine likely candidates for the structure of ground state of Mo₂C₈,a number of possible isomeric structures were investigated.The most stable structure is found to possess C_2h symmetry,where two Mo atoms connect directly each other and each Mo atom connects to four carbon atoms,Mo atom is enclosed by Catoms,so as the spatial effect and bond forming property are concerned,the reactions of Mo₂C₈^- with NH₃,H₂O are difficult.In fact,experiment had observed Mo₂C₈^- ion are indeed completely unreactive with NH₃ and H₂O.Furthermore,our calculated EAof this isomer is 3.6 eV,which is just the upper limit of the experimental value(the experimental value of E_A(Mo₂C₈) is between 2.7±0.2 eVand 3.3±0.3 eV),and this structure can also explain other existing experimental results perfectly.

Key words: Mo₂C₈ cluster, Geometric configuration, Electronic structure