Argentophillic interactions in argentum chalcogenides: First principles calculations and topological analysis of electron density.

The plasticity of Ag2 S and Ag2 Se crystals important for applications is associated mainly with AgAg metallophilic bonds, which are related to van der Waals interactions and therefore are not directed. This is demonstrated by the first principles DFT M06 LCAO calculations of Ag2 X (X = S, Se) crystals (periodic model) and hypothetical molecules Xn Ag2n (X = S, Se; n = 1, 2, 4) in gas phase (molecular model). A topological analysis of the calculated electron density, was performed both for periodic and molecular models of Ag2 X (X = S, Se). It was found that Ag-Ag interatomic distances are close in periodic and molecular models. The numerical values of electron density, its Laplacian, kinetic, and potential energy densities are also close in both models and confirm the existence of AgAg metallophilic bonds.