Hg-Hg bonding and its influence on the stability of (HgS) clusters

Pulsed laser ablation of a HgS_(s) precursor shows the formation of small cluster ions, (HgS)⁺, together with HgS^± and [(HgS) + S]^±. The computed structure, atomization energy, and HOMO-LUMO gap energy values of the lowest energy ring singlet show stable (HgS). However, the computed bond conductance of the Hg-Hg bond in (HgS) shows a high value for (HgS) (ξ = 1.072-0.122), whereas it is low for (HgS) (ξ = 0.039-0.006) and decreases significantly as the ring expands, indicating that (HgS) is unstable. It evidences that the weak chemical bonding between Hg²⁺-Hg²⁺ closed shell (5d¹⁰-5d¹⁰) electrons plays a significant role in the stability of ring (HgS). Thus, it validates the experimental observation of stable cluster ions up to (HgS)₄⁺. In contrast, the low energy chain triplet (HgS) shows a progressive increase in stability and bond conductance with chain length, indicating sustained mercurophilic interactions in long chain clusters like its crystal structure. Furthermore, the lowest/low energy isomers of HgS have been computed for their energetics, HOMO-LUMO gaps, and electron affinity using DFT-B3LYP/PBE0 methods.