Molecular dynamics simulations of sodium nanoparticle deposition on magnesium oxide

TL;DR

This study uses molecular dynamics simulations to investigate how sodium nanoparticles deposit on magnesium oxide surfaces, revealing insights into energy relaxation, structural evolution, and the effects of deposition energy.

Contribution

It introduces a new empirical force field for sodium-magnesium oxide interactions and explores nanoparticle dynamics over long timescales, bridging experimental observations and theoretical modeling.

Findings

Nanoparticle structure varies with deposition energy.

Energy relaxation occurs over hundreds of picoseconds.

Deposition outcomes range from soft landing to fragmentation.

Abstract

The interaction of mass-selected atomic clusters and nanoparticles with surfaces attracts strong interest in view of fundamental research and technological applications. Understanding dynamics of the deposition process is important for controlling structure and functioning of deposited nanoparticles on a substrate, but experimental techniques can usually observe only the final outcome of the deposition process. In this paper, the deposition of 4 nm-sized sodium nanoparticles on an experimentally relevant magnesium oxide substrate is studied by means of classical molecular dynamics simulations. An empirical force field is derived which accounts for the interaction of highly polarizable Na atoms with the surface, reproducing the results of previously reported quantum mechanics/molecular mechanics simulations. Molecular dynamics simulations permit exploring the dynamics of deposited nanoparticles on long timescales on the order of hundreds of picoseconds, thus enabling the analysis of energy relaxation mechanisms and the evolution of nanoparticle structure up to its thermalization with the substrate. Several nanoparticle characteristics, such as internal structure, contact angle, and aspect ratio are studied in a broad deposition energy range from the soft landing to multi-fragmentation regimes.