title: Theoretical study of the structure of self-assembled monolayers of short alkylthiolates on Au(111) and Ag(111): the role of induced substrate reconstruction and chain-chain interactions.
abstract: We compare the stability of various structures of high coverage self-assembled monolayers (SAMs) of short alkylthiolates, S(CH(2))(n-1)CH(3) (= C(n)), on Ag(111) and Au(111). We employ: (i) the ab initio thermodynamics approach based on density functional theory (DFT) calculations, to compare the stability of SAMs of C(1) (with coverages Θ = 3/7 and 1/3) on both substrates, and (ii) a set of pairwise interatomic potentials derived from second-order Møller-Plesset (MP2) perturbation theory calculations, to estimate the role of chain-chain (Ch-Ch) interactions in the structure and stability of SAMs of longer chain alkylthiolates. For C(1)/Ag(111) (C(1)/Au(111)) the SAM with Θ = 3/7 is more (less) stable than for Θ = 1/3 in a wide range of temperatures and pressures in line with experiments. In addition, for the molecular densities of SAMs corresponding to Θ = 3/7 and 1/3, the MP2-based Ch-Ch interaction potential also predicts the different chain orientations observed experimentally in SAMs of alkylthiolates on Ag(111) and Au(111). Thus, for short length alkylthiolates, a simple model based on first principles calculations that separately accounts for molecule-surface (M-S) and Ch-Ch interactions succeeds in predicting the main structural differences between the full coverage SAMs usually observed experimentally on Ag(111) and Au(111).
authors.affiliation: Laboratorio de Colisiones Atómicas, Facultad de Ciencias Exactas Ingeniería y Agrimensura, Universidad Nacional de Rosario (UNR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Pellegrini 250 (2000) Rosario, Argentina.
authors.forename: P N
authors.initials: PN
authors.lastname: Abufager
authors.forename: J G
authors.initials: JG
authors.lastname: Solano Canchaya
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Alcamí
authors.forename: F
authors.initials: F
authors.lastname: Martín
authors.forename: L
authors.initials: L
authors.lastname: Alvarez Soria
authors.forename: M L
authors.initials: ML
authors.lastname: Martiarena
authors.forename: K
authors.initials: K
authors.lastname: Reuter
authors.forename: H F
authors.initials: HF
authors.lastname: Busnengo