ReaxFF Simulations of Self-Assembled Monolayers On Silver Surfaces and Nanocrystals

TL;DR

This study uses ReaxFF molecular dynamics to simulate self-assembled monolayers of alkane thiolates on silver surfaces and nanoparticles, revealing stable structures and adsorption behaviors consistent with experimental data.

Contribution

It demonstrates the application of reactive force fields to large-scale simulations of SAMs on silver, capturing structural details and reorganization phenomena.

Findings

Stable (sqrt(7) x sqrt(7))R19.1° assemblies observed

Nanoparticles smaller than 4 nm show core restructuring

Preferred adsorption site is on-top, matching experiments

Abstract

The self-assembled monolayers of alkane thiolates on Ag (111) surfaces and nanoparticles are studied using molecular dynamics. Reactive force fields allow simulations of very large systems such as nanoparticles of 10 nm. Stable (sqrt(7) X sqrt(7))R19.1{\deg} assemblies are obtained as experimentally observed for these systems. Only nanoparticles smaller than 4 nm show a spontaneous restructuration of the metallic core. The preferred adsorption site is found to be in an on-top position, in good agreement with recent X-ray absorption near edge structure experiments. Moreover, similar distances between the sulfur headgroups are found on the facets and edges.