validation study of the computational protocol for predicting the optical properties of
Monolayer-Protected metal Clusters (MPCs) using time-dependent density-functional theory is
presented. The Au25(SC2H4Ph)18− MPC is chosen as a reference, due to the availability of both
structural and optical experimental data. The effects of the geometry, the basis set, the
exchange-correlation functionals, and the use of simplified or experimental ligands on the optical
properties of Au25(SC2H4Ph)18− are discussed critically. When such options are carefully
selected, an almost quantitative matching between theory and experiment is obtained. Noteworthy,
the use of a precise geometric structure proves to be both crucial and critical for an
accurate prediction of the optical response of MPC systems, a feature which is not easy to
achieve using current density-functional theory approaches.
