Structure and bonding in silver halides. A quantum chemical study of the monomers: Ag2X, AgX, AgX2, and AgX3 (X = F, Cl, Br, I)

摘要

The molecular structure of all silver halide monomers, Ag2X, AgX, AgX2, and AgX3, (X = F, Cl, Br, I), have been calculated at the B3LYP, MP2, and CCSD(T) levels of theory by using quasi relativistic pseudopotentials for all atoms except fluorine and chlorine. All silver monohalides are stable molecules, while the relative stabilities of the subhalides, dihalides, and trihalides considerably decrease toward the larger halogens. The ground-state structure of all Ag2X silver subhalicles has C-2V symmetry, and the molecules can be best described as [Ag-2]X-+(-) Silver dihalides, are linear molecules; AgF2 has a 2 Sigma(g) ground state, while all of the other silver dihalides have a ground state of 2 Pi(g) symmetry. The potential energy surface (PES) of all silver trihalides has been investigated. Neither of these molecules has a D-3h symmetric trigonal planar geometry, due to their Jahn-Teller distortion. The minimum energy structure of AgF3 is a T-shaped structure with C-2v symmetry. For AgCl3, AgBr3, and Agl(3), the global minimum is an L-shaped structure, which lies outside the Jahn-Teller PES. This structure can be considered as a donor-acceptor system, with X-2 acting as donor and AgX as acceptor. Thus, except for AgF3, in the other three silver trihalides, silver is not present in the formal oxidation state 3.