Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Statistical Physics (general)

DY 13.2: Vortrag

Montag, 7. März 2016, 15:15–15:30, H48

Determining the size at which neutral gold clusters turn three-dimensional at finite temperature — •Bryan Goldsmith¹, André Fielicke², Matthias Scheffler¹, and Luca Ghiringhelli¹ — ¹Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany — ²Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin

Discerning the ground state structure of free gold clusters, and in particular the critical size when Au clusters begin favoring three-dimensional (3D) structures over planar structures at 0 K, has been a topic of longstanding interest. At finite temperature, however, Au clusters exhibit coexistence of many structural isomers. To move beyond the monostructure description of clusters at 0 K, we performed ab initio replica-exchange molecular dynamics (REMD) on Au_n clusters (n=5-14) to identify metastable states, their relative stability, and to examine the influence of entropy and van der Waals (vdW) on the isomer energetics. REMD calculations used PBE with the scalar ZORA correction and either Tkatchenko-Scheffler or Many-Body-Dispersion vdW. Free energies of Au isomers are estimated using the Multistate Bennett Acceptance Ratio and the planar and 3D isomer populations are examined between 100-1000 K. The distribution of bond coordination numbers is used to discriminate isomers along the dynamical trajectories. Isomer energetic ordering is verified using renormalized second-order perturbation theory. Computed anharmonic IR spectra of Au_n are compared with experimental spectra.