Benchmarking of CCSD(T)/CBS Binding Energies and Density Functional Theory Performance for Small Arsine Clusters (ash3)n (n = 2–6): Unraveling the Delicate Balance Between Weak Hydrogen Bonding and Dispersion Interactions

Arsine (AsH3) clusters—heavy Group 15 hydride systems of critical importance in semiconductor manufacturing and atmospheric arsenic chemistry—lack rigorous high-accuracy ab initio quantification of their binding energetics, hindering the development of reliable computational methods for larger arsenic-containing systems. Here we present a systematic investigation of the structures and binding energies of arsine clusters ranging from dimers to hexamers, employing a validated composite scheme to establish benchmark energies at the CCSD(T)/CBS (coupled-cluster singles, doubles, and perturbative triples extrapolated to the complete basis set) limit. We further evaluate the performance of ten density functional theory functionals spanning hybrid, dispersion-corrected, and long-range corrected categories against our benchmark dataset. Our results reveal that dispersion interactions contribute nearly 40