SKM 2023 – scientific programme
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O: Fachverband Oberflächenphysik
O 57: Focus Session: Semiconductor Surface Chemistry – from Reaction Mechanisms to Well-Ordered Interfaces II
O 57.6: Talk
Wednesday, March 29, 2023, 16:45–17:00, GER 38
Ab initio description of surface restructuring and phase boundaries under realistic conditions — •Yuanyuan Zhou1,3, Chunye Zhu1,2, Matthias Scheffler1, and Luca M Ghiringhelli1 — 1The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft and IRIS-Adlershof of the Humboldt-Universität zu Berlin — 2School of Advanced Manufacturing, Guangdong University of Technology, Jieyang 515200, China — 3Department of Physics, Technical University of Denmark, Kongens Lyngby, 2800, Denmark
A reliable description of surfaces equilibria in a reactive gas is a prerequisite for understanding mechanism of heterogeneous catalysis. However, studying phase equilibria at ab initio level, is a formidable challenge, especially for systems with sluggish barriers. In this work [Zhou et al. Phys. Rev. Lett. 128, 246101(2022)], we introduce a fully ab initio approach to determine temperature-pressure (T−p) surface phase diagram and to evaluate phase equilibria of surfaces in a gas phase. For this purpose, our replica-exchange grand-canonical (REGC) method [Zhou et al. Phys. Rev. B. 100, 174106(2019)], is extended by evaluating the heat capacity, Cv(T, p), as function of T and p, thus locating phase boundaries where Cv(T, p) shows ridges. The approach is demonstrated by addressing open questions for the Si(100) surface in a H2 gas phase. 25 distinct stable surface phases are identified, most of which have not been observed experimentally, so far. The results also show that Si-Si-bonds forming/breaking is the driving force behind the experimentally 3×1 and 2×1 phase transition.