Molecular dynamics simulations of palladium cluster growth on flat and rough graphite surfaces

TL;DR

This study uses molecular dynamics simulations to analyze how surface roughness and defects on graphite influence palladium cluster growth, affecting cluster structure, density, and growth kinetics.

Contribution

It provides new insights into how surface roughness and defects alter palladium cluster growth mechanisms and structures on graphite surfaces.

Findings

Rough surfaces reduce cluster size and density.

Defects induce cluster interactions altering growth.

Growth follows a power law with kinetic energy dependence.

Abstract

Parallel Molecular Dynamics simulations are conducted for describing growth on surfaces with different kind of roughness: a perfect ordered crystalline flat graphite surface, a disordered rough graphite surface and flat surface with an ordered localized defect. It is shown that disordered rough surfaces results in a first step to reduction of the sticking coefficient, increased cluster density, size reduction. Structure of the clusters shows the disappearance of the octahedral site characteristic of compact structure. Isolated defect induces cluster-cluster interactions that modify growth compared to perfect flat surface. Kinetic study of growth shows power law tαz evolution for low impinging atom kinetic energy. Increasing kinetic energy, on all kinds of surfaces, results in a slightly larger exponent z, but fitting by an exponential function is quite good too. Lattice expansion is favoured on rough surfaces but increasing incoming atom kinetic energy weakens this effect.