Unveiling the structural and electronic properties of the neutral and anionic gallium sulfide clusters

Abstract

The structural and electronic properties of the neutral gallium sulfide (GaS2, Ga2S2, GaS4, and Ga 2S4) clusters along with their anionic counterparts have been investigated systematically using the density functional theory, the second-order Møller-Plesset perturbation theory (MP2), and coupled cluster singles and doubles, including noniterative triples [CCSD(T)] with the 6-311+G(2df) basis set. At the CCSDT(T)//MP2 level, the lowest-energy configurations of the gallium sulfides prefer to be cyclic (GaS2), linear (GaS2 -), kite shape with a thiozonide unit (GaS4 and GaS4 -), rhombic (Ga 2S2 and Ga2S2 -), and planar with two sulfur atoms in a terminal position (Ga2S4 and Ga2S4 -) geometries. In the gallium-sulfur binary clusters considered in this study, the neutral and anionic ground-state geometries prefer the planar structures with alternation of gallium and sulfur atoms. All the neutral clusters, with the exception of Ga2S 2, possess high electron affinities, which range from 3.51 to 3.64 eV at the CCSDT(T)//MP2 level. A sequential addition of a sulfur atom to the Ga2S n (n = 1-3) system increases the charge transfer from gallium atoms to sulfur atoms, the adiabatic electron affinity, and the HOMO-LUMO gap. The sufficiently large HOMO-LUMO gaps ensure the stability of these gallium sulfide clusters. The Ga2S4 → Ga 2S2 + S2 process is the most thermodynamically favored toward dissociation.