Geometries and electronic structures of alkaline earth auride clusters, Au₄M (M = Mg, Ca, Sr, Ba)

Using density functional theory calculations we have investigated the geometries and electronic structures of a series of neutral alkaline earth auride clusters with chemical formula Au₄M, with M = Mg, Ca, Sr, and Ba. These clusters are formally made of an Au₄^2- unit and a doubly-charged M²⁺ cation. Of the three geometries investigated herein, namely planar, square-pyramidal, and lantern-type geometry, the planar structure is the most energetically favored. Because all structures are characterized by positive vibrational frequencies, these clusters represent local minima on the corresponding potential energy hypersurtace.