(63i) Atomistic Force Field Model Development for the Thiolate/Defective Au (111) Interface

A molecular-level understanding of the interplay between self-assembled monolayers (SAMs) of thiolates and gold is of great importance to a wide range of potential applications in surface science and nanotechnology. The surface properties of SAMs are largely determined by the structure and chemistry of the thiolate-gold interface. Despite theoretical research progress of the past decade, an atomistic model, capable of describing key features of SAMS at defective gold surfaces, is still missing. In this work, by means of periodic ab initio density functional theory (DFT) calculations, we have developed a new atomistic force field model for ethylthiolate SAMs on the defective Au (111) surface. In particular, new force field parameters were carefully trained to reproduce characteristic ethylthiolate configurations of the bridge and staple motifs: the non-bonded interactions were derived following the Optimized Potential for Liquid Simulations (OPLS) force field and the paper by Rai et al.;¹ the bonded force field parameters were extensively fitted via a comparison between DFT and molecular dynamics calculations, until a good match has been achieved, for vibration spectra for bonds and angles, for torsional energy profile for dihedral angles. Such atomistic force field model development will provide a new fundamental understanding of SAM/gold models and add advancement to existing interface research knowledge.

Reference

1. Rai, B.; Sathish, P.; Malhotra, C. P.; Pradip; Ayappa, K. G., “Molecular Dynamic Simulations of Self-Assembled Alkylthiolate Monolayers on an Au(III) Surface”, Langmuir, 2004, 20, 3138.