Structure and stability of coinage metal fluoride and chloride clusters (MnFn and MnCln, M = Cu, Ag, or Au; n = 1-6).

Calculations in the framework of the density functional theory are performed to study the lowest-energy isomers of coinage metal fluoride and chloride clusters (M(n) F(n) , M(n) Cl(n) , M = Cu, Ag, or Au, n = 1-6). For all calculated species starting from the trimers the most stable structures are found to be cyclic arrangements. However, planar rings are favored in the case of metal fluorides whereas metal chlorides prefer nonplanar cycles. Calculated bond lengths and infrared frequencies are compared with the available experimental data. The nature of the bonding, involving both covalent and ionic contributions, is characterized. The stability and the fragmentation are also investigated. Trimers are found to be particularly stable when considering the Gibbs free energies.