Benchmarking density functional and basis set combinations for anionic gold clusters Aun– (n = 1–20): a combined theoretical and photoelectron spectroscopic study

Reliable theoretical description of anionic gold clusters remains challenging because the energetic ordering of low-lying isomers is highly sensitive to the exchange-correlation functional, basis set, and relativistic treatment. In this study, we systematically benchmarked functional-basis set combinations for Au n − ( n = 1–20) by comparing optimized low-lying structures and simulated photoelectron spectra (PES) with available experimental data. An initial screening of 14 functionals (B3LYP, B3PW91, CAM-B3LYP, O3LYP, X3LYP, HSE06, M06, M06-L, M06-2X, PBE0, PBE, TPSSh, TPSS, and revTPSS) with six basis sets (LANL2DZ, SDD, dhf–TZVPP, dhf–QZVPP, def2–QZVPP, and aug–cc–pVTZ–PP) identified Au 5 − , Au 10 − , and Au 12 − as key test cases. Both revTPSS/SDD and revTPSS/LANL2DZ reproduced the literature-supported ground-state assignments for the three benchmark clusters, with comparable agreement between calculated and experimental vertical detachment energies (VDEs). This scheme was then applied to Au n − ( n = 1–20) to determine ground-state structures and electronic properties. The simulated PES and calculated VDEs reproduce the main experimental size-dependent features, including the overall spectral evolution, the even–odd alternation of VDEs, the two-dimensional (2D)-to-three-dimensional (3D) crossover at Au 12 − , and the exceptional stability of Au 20 − . These results support revTPSS/SDD as a practical computational approach for the structural assignments and detachment properties of the bare gold-cluster anions examined here.