title: Calculation of One- and Two-Photon Absorption Spectra of Thiolated Gold Nanoclusters using Time-Dependent Density Functional Theory.
abstract: The one- (OPA) and two-photon (TPA) absorption spectra have been calculated for a gold dimer, for a monothiolated gold dimer anion, for a thiolated gold cluster [Au25(SH)18](-1), whose structure has been determined, and for a proposed cluster [Au12(SR)9](+1) using time-dependent density functional theory (TDDFT). Geometry optimization with different exchange-correlation (X-C) functionals yielded small differences which had significant consequences in the spectra calculations. The calculated excitation energies of Au25(SH)18(-1) are in excellent agreement with experiment when the local density approximation Xα-optimized geometry is used with the B3LYP X-C functional. The CAMB3LYP and mCAM functionals yielded OPA results in good agreement with experiment for the dimer systems and the larger clusters. The super-atom theory was useful in analyzing the electronic transitions in the larger clusters. TPA was dominated by resonance effects, and the calculated cross-sections displayed a strong X-C functional dependence.
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, General Dynamics Information Technology, Inc., 5200 Springfield Street, Dayton, Ohio 45431, and UES, Inc., 4401 Dayton Xenia Road, Dayton, Ohio 45432.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Day
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, General Dynamics Information Technology, Inc., 5200 Springfield Street, Dayton, Ohio 45431, and UES, Inc., 4401 Dayton Xenia Road, Dayton, Ohio 45432.
authors.forename: Kiet A
authors.initials: KA
authors.lastname: Nguyen
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio 45433, General Dynamics Information Technology, Inc., 5200 Springfield Street, Dayton, Ohio 45431, and UES, Inc., 4401 Dayton Xenia Road, Dayton, Ohio 45432.
authors.forename: Ruth
authors.initials: R
authors.lastname: Pachter