Atomistic simulation of alkanethiol self-assembled monolayers on different metal surfaces via a quantum, first-principles parametrization of the sulfur-metal interaction

A detailed investigation of the effect of the substrate on the structure and conformation of alkanethiol self-assembled monolayers is presented through detailed atomistic simulations based on a first-principles density functional modeling of the sulfur-metal interaction. Ab initio calculations on a methanethiol molecule adsorbed on different metal surfaces (gold, silver, and platinum) are conducted, and the data obtained are used to develop an accurate classical force field for the sulfur-metal interaction. This serves as input to a very efficient Monte Carlo algorithm with which detailed atomistic simulations are carried out with a number of model alkanethiol self-assembled monolayers (SAMs) adsorbed on the three different substrates. Emphasis is given primarily to the study of the effect of the substrate on the structural properties of the simulated alkanethiol SAMs, such as molecular orientation, molecular conformation, and statistics of gauche defects, as a function of their chain length.