Structure of self-assembled monolayers of alkylthiolates on Au(111) and Ag(111): a comparative study based on Density Functional and post Hartree-Fock calculations

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

Workshop; Passion for knowledge; 2010

  We present a comparative study of the relative stability of various structures 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].[1] J. C. Love, L. A. Estroff, J. K. Kriebel, R. G. Nuzzo, and G. M. Whitesides, Chem.Rev. 105, 1103 (2005); C. Vericat, M. E. Vela, J. A. M. Gago, X. Torrelles, and R. C.Salvarezza, J. Phys.: Condens. Matter 18, R867 (2006); D. P. Woodruff, Phys. Chem.Chem. Phys. 10, 7211 (2008).[2] J. G. Solano Canchaya, Y. Wang, M. Alcamí, F. Martín and H. F. Busnengo, Phys.Chem. Chem. Phys. 12, 7555 (2010).[3] P.N. Abufager, L. Alvarez Soria, M.L. Martiarena, K. Reuter, and H.F. Busnengo (submitted).