Dresden 2017 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 27: Surface Dynamics: Theory

O 27.6: Vortrag

Dienstag, 21. März 2017, 12:00–12:15, TRE Phy

Replica-Exchange Grand-Canonical Algorithm for Determining Phase Diagrams of Surfaces in Reactive Atmospheres — •Yuanyuan Zhou, Luca M. Ghiringhelli, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

A temperature-pressure phase diagram describes the composition and structure of a system at thermal equilibrium and is an essential tool for understanding material properties. The atomistic thermodynamics (AT) approach has been very successful in predicting phase diagrams for surfaces [K. Reuter, M. Scheffler, PRL 90, 046103 (2003)] and gas-phase clusters [S. Bhattacharya et al., PRL 111, 135501 (2013)] at realistic T,p conditions. However, its limitation is the lack of an unbiased sampling of the configurational space. Here, we present a novel replica-exchange (RE) grand-canonical (GC) Monte-Carlo (MC) algorithm that allows for the efficient estimate of the partition function of atomistic systems. We specifically target open systems in the GC ensemble, aiming at describing (nano)structured surfaces in a reactive atmosphere (e.g., for heterogeneous catalysis) at realistic T,p. RE allows for an efficient sampling by shuttling configurations from regions of low T or high chemical potential (µ) to regions of high T or low µ. In order to demonstrate the approach, we apply REGC-MC to a two-component Lennard-Jones system with a surface in contact with a gas-phase. In particular, we discuss REGC-MC’s viability by comparing our results with calculated ones using AT and find good agreement at low coverage but quite different at relatively high coverage.