Heterometal-Controlled Electron-Vibration Coupling and Carrier Relaxation Dynamics in Au3M2 (M = Cu, Ag) Nanoclusters.

Understanding how heterometal substitution regulates excited-state dynamics is essential for designing atomically precise nanoclusters. Here, we combine time-dependent density functional theory and nonadiabatic molecular dynamics to investigate Au3M2 (M = Cu, Ag) nanoclusters. Despite nearly identical geometries, Ag-to-Cu substitution markedly alters their electronic structures and vibrational properties. Au3Ag2 maintains a symmetric superatomic electronic structure with a closed-shell 1S2 configuration, whereas Au3Cu2 exhibits reduced symmetry and more localized frontier orbitals. Consequently, the two clusters display distinct relaxation pathways. Au3Cu2 undergoes faster ultrafast relaxation from the higher excited state to the intermediate state (71 fs), while Au3Ag2 exhibits more rapid relaxation to the LUMO (4.6 ps) and a longer electron-hole recombination lifetime (53 ns). Analysis of energy-gap fluctuations indicates that these differences originate from distinct electron-vibration coupling associated with core and ligand motions. These results clarify how heterometal substitution governs carrier dynamics in atomically precise nanoclusters.