Multiscale modelling of structure formation of C$_{60}$ on insulating CaF$_2$ substrates

TL;DR

This paper develops a multiscale modeling approach combining molecular dynamics and force fields to systematically derive transition rates for simulating the growth of C60 molecules on CaF2 substrates, addressing limitations of experimental data.

Contribution

It introduces a bottom-up method to accurately determine transition rates for kinetic Monte Carlo simulations of molecular film growth, specifically for buckminsterfullerene on calcium fluoride.

Findings

Derived explicit transition rate expressions from molecular dynamics

Developed classical force fields for C60 and CaF2

Enabled more accurate long-term growth simulations

Abstract

Morphologies of adsorbed molecular films are of interest in a wide range of applications. To study the epitaxial growth of these systems in computer simulations requires access to long time and length scales and one typically resorts to kinetic Monte Carlo (KMC) simulations. However, KMC simulations require as input transition rates and their dependence on external parameters (such as temperature). Experimental data allows only limited and indirect access to these rates, and models are often oversimplified. Here we follow a bottom-up approach and aim to systematically construct all relevant rates for an example system that has shown interesting properties in experiments, buckminsterfullerene on a calcium fluoride substrate. We develop classical force fields (both atomistic and coarse-grained) and perform molecular dynamics simulations of the elementary transitions in order to derive explicit expressions for the transition rates with a minimal number of free parameters.