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O: Fachverband Oberflächenphysik

O 107: Semiconductor Surfaces (joint session O/HL)

O 107.6: Vortrag

Donnerstag, 19. März 2020, 16:30–16:45, REC C 213

Determining surface phase diagrams including anharmonic effects — •Yuanyuan Zhou, Matthias Scheffler, and Luca Ghiringhelli — Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin-Dahlem, Germany

A prerequisite for analyzing and understanding the electronic properties and the function of surfaces is the detailed knowledge of their structure under realistic conditions. We have developed a replica-exchange grand-canonical (REGC) algorithm that enables the unbiased calculation of pressure-temperature phase diagrams of surfaces or clusters in reactive atmospheres including anharmonic effects. [1] Moreover, the multi-canonical sampling yields the temperature-pressure dependence (map) of all equilibrium observables that can be measured within the given model Hamiltonian. For instance, structural parameters such as the radial distribution function, or the HOMO-LUMO gap. This allows for rational design, where operando condition are taking fully into account. Our approach is demonstrated by studying Si clusters and the Si(100) surface in a hydrogen atmosphere, by coupling REGC with ab initio molecular dynamics. All interactions are described at the density-functional-theory level, with the Perdew-Burke-Ernzerhof gradient-corrected exchange-correlation functional. In particular, we show how to determine observable structures at finite temperature and pressure, i.e., obtained by ensemble averaging the sampled structures.

[1] Y. Zhou, M. Scheffler, and L. M. Ghringhelli, Phys. Rev. B. 100, 174106 (2019).