Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 14: Oxide Surfaces: Adsorption and Reactivity

O 14.9: Vortrag

Montag, 16. März 2015, 17:00–17:15, MA 042

Formation of 1D adsorbed water structures on CaO(001) — Xunhua Zhao, •Sergey V. Levchenko, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, DE

Understanding the interaction of water with oxide surfaces is of fundamental importance for basic and engineering sciences. Recently, a spontaneous formation of one-dimensional (1D) adsorbed water structures have been observed on CaO(001) [1]. Interestingly, at other alkaline earth metal oxides, in particular MgO(001) and SrO(001), such structures have not been found experimentally. We calculate relative stability of adsorbed water structures on the three oxides using density-functional theory with the hybrid functional HSE06 and ab initio many-body dispersion interaction correction [2], combined with the ab initio atomistic thermodynamics. Low-energy structures at coverages up to one monolayer are obtained with a first-principles genetic algorithm. Finite-temperature anharmonic vibrational spectra are calculated using ab initio molecular dynamics. We find a range of (T, p) conditions where 1D structures are thermodynamically stable on CaO(001). The orientation and vibrational spectra of the 1D structures are in agreement with the experiments [1]. The formation of the 1D structures is found to be actuated by a symmetry breaking in the adsorbed water tetramer, as well as by a balance between water-water and water-substrate interactions, determined by the lattice constant of the oxide.—[1] X. Shao, Y. Fujimori, M. Sterrer, H.-J. Freund, and N. Nilius, to be published; [2] A. Tkatchenko, R. A. DiStasio, Jr., R. Car and M. Scheffler, Phys. Rev. Lett. 108, 236402 (2012).