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Au/H similarity is a hot topic in chemistry recently.1-3 Here we report on theoretical prediction of the new members of Au/H analogy family: GaAun and Ga2Aun.A systematic density functional theory and wave function theory investigation on the geometrical and electronic properties of GaAun 0/-and Ga2Aun 0/-(n=1-4)clusters has been performed in this work.Detailed orbital analyses,adaptive natural density partitioning(AdNDP)4 and electron localization function(ELF)analyses5 have been performed and discussed.GaAun-anions prove to possess linear C∞v GaAu-(2Σ+),V-shaped C2v GaAu2-(1A1),planar triangular D3h GaAu3-(2A1)and perfect tetrahedral Td GaAu4-(1A1).Their neutrals GaAun favor the same geometry,except GaAu4: linear C∞v GaAu(1Σ+),V-shaped C2v GaAu2(2B2),planar triangular D3h GaAu3(1A1)and severely distorted Cs GaAu4(2A).Gallium aurides appear to be analogous to the corresponding gallium hydrides6,except neutral GaAu4.Ab initio theoretical evidence strongly suggests that bridging gold7-9 atoms exit in the ground states of C2v Ga2Au-(3B1),C2v Ga2Au(2B1),C2v Ga2Au2-(2A1),C2v Ga2Au2(1A1),D3h Ga2Au3-(1A1),D3h Ga2Au3(2A1),C3v Ga2Au4-(2A1)and C3v Ga2Au4(1A1),which prove to possess an Ga-Au-Ga bridging bond.Different from Ga2Aun(n=1-3),C3v Ga+(GaAu4)-is predicted to be of a saltlike composition10 with three Ga-Au-Ga 3c-2e bonds.The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations.Bridging gold addressed in this work provides an interesting bonding mode for the covalent and ionic deficient systems and may aid in designing new materials and catalysts with highly dispersed Au atoms.