Structure of self-assembled monolayers of alkylthiolates on Au(111) and Ag(111): a study based on ab-initio calculations

P. N. ABUFAGER; J. SOLANO CANCHAYA; Y. WANG; L. ALVAREZ SORIA; M. ALCAMÍ; F. MARTÍN; K. REUTER; M.L.MARTIARENA; H.F.BUSNENGO

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Congreso; 10 European Conference on Surface and Crystallography and Dynamics; 2010

We present a comparative study of the relative stability of variousstructures of high coverage (standing-up) self-assembled mono-layers (SAMs) [1] of alkylthiolates  on Ag(111) and Au(111) based on: i) Density Functional Theory (DFT) calculations to evaluate the S-substrate interaction and ii) a chain-chain interaction potential, recently derived from second order Møller-Plesset (MP2) calculations for alkanethiols in gas phase [2]. For both substrates we consider the two possible surface coverages observed experimentally for Ag(111) and Au(111): i.e. 3/7 and 1/3 respectively. For methylthiolate/Ag(111), we report a new possible structure for coverage 3/7, involving top-most layer surface Ag atom vacancies (more stable than the most stable one found so far, corresponding to the unreconstructed surface) characterized by various structural parameters in excellent agreement with experiments [3]. Our calculations successfully account for the coverage observed for the shortest chain alkylthiolates as well as the experimental tilt angle of longer chain alkylthiolates on both substrates [1].References[1] Love J. C., Estroff L. A., Kriebel J. K., Nuzzo R. G., and Whitesides G. M., Chem. Rev. (2005), 105, 1103;Vericat C., Vela M. E., Gago J. A. M., Torrelles X., andSalvarezza R. C., J. Phys.: Condens. Matter (2006), 18,R867; Woodruff D. P., Phys. Chem. Chem. Phys. (2008), 10, 7211.[2] Solano Canchaya J. G., Wang Y., Alcamí M., Martín F. and Busnengo H. F., Phys. Chem. Chem. Phys.(2010), 12, 7555.[3] Abufager P.N., Alvarez Soria L., Martiarena M.L., Reuter K., and Busnengo H.F. (submitted).