Recent STM experiments have reported a strange behavior of chiral organic molecules when adsorbed on a metal surface at around 400K, (R,R) tartaric acid molecules adsorbed on Cu(110) formed one thermally stable and asymmetrical superstructure, in which tartarate trimers extend in rows along the [-114] direction[1]. We believe that the interactions between the tartarates forming the trimers are very directional where the OH groups are playing a main role. The directionality also depends on the chirality of the molecules as the same experiments on (S,S) tartaric acid molecules form trimers growing along the [1-14] direction. In this study we focus on (R,R) tartaric acid molecules and we aim at an atomistic understanding of the nature of this intriguing ordering process, which appears as a suitable model system for the development of future enantio-selective heterogeneous catalysts. In the first step we use density-functional theory to accurately characterize the molecule-surface system on the microscopic level. The resulting energetics is then employed to parameterize a lattice gas Hamiltonian, which subsequently enables to address the mesoscopic ordering behavior at finite temperatures by means of Monte Carlo simulations [2].
[1] V. Humblot, M.O. Lorenzo, G.J. Baddeley, S. Haq and R. Raval J. Am. Chem. Soc. 126, 6460 (2004)
[2] K. Reuter, C. Stampfl, and M. Scheffler, "Ab initio atomistic thermodynamics and statistical mechanics of surface properties and functions" in: Handbook of Materials Modeling, Vol. 1, (Ed.) S. Yip. Kluwer, Dordrecht (2005)
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