Atomistic modeling of epitaxial graphene on Ru(0001) and deposited ruthenium nanoparticles

Abstract

A bond-order potential is presented for the Ru-C system, aiming to model epitaxial graphene on Ru(0001) and ruthenium nanoparticles on such substrates or on graphite. The model has been parametrized on electronic structure calculations and improved to account for long-range London dispersion forces following an approach similar to the Grimme D2 correction scheme, as well as possible nonadditive screening effects that are relevant for epitaxial graphene on metal. The model correctly reproduces a variety of structural properties for different commensurate moiré structures as observed in experiments or predicted by density-functional theory calculations, although limitations are noted for very small adsorbates likely due to the lack of explicit charge transfer. The energetic and thermal stabilities of Ru nanoparticles on graphite and epitaxial graphene have been addressed using local optimizations and molecular dynamics simulations. While the nanoparticles exhibit relatively fast diffusion on the graphite substrate, the corrugation of epitaxial graphene strongly stabilizes them against internal rearrangement and global diffusion. The simulated vibrational spectra of epitaxial graphene show variations with the moiré structure and temperature that provide insight into anharmonicities and emphasize the role of strain.

Depressions by stacking faults in nanorippled graphene on metals

“…We use instead BOP calculations that allow thousands of atoms to be treated (SI). A BOP potential has in fact been carefully parametrized for the Ru-C system against the results of DFT calculations, and it was found to satisfyingly reproduce the structural parameters of the nanorippled graphene/Ru(0001) moiré [39]. Interestingly, (0001)-terminated Ru and Re have strong electronic similarities, with in both cases d bands in the 2-4 eV range below the Fermi level [65,66,67].…”

A mesoscopic model of nanoclusters self-assembly on a graphene Moiré

“…The spatial footprint of the clusters computed by KMC modeling [15] resembles a small red dot-like clusters that cover a single Moiré cell taken from our Figures 11(b) and 12(b), that is, only a fraction of the full evolution time interval to equilibrium was accessed in the KMC modeling. MD simulations [16] were limited to an even smaller, in fact, a tiny time interval of 5.5 ns, which only allowed to evaluate the effective diffusion constant by calculating the mean square displacement of the center of mass of the initial atomic configuration.…”

“…Also, this method of epitaxial self-assembly is gaining popularity for organic substances (as reviewed in [13]) and C60 molecules [14]. Despite significant advances in experiment, modeling and computation of guided self-assembly on graphene to-date is limited to a handful of KMC and molecular dynamics studies [15,16].…”

Combined atomistic simulations to explore metastability and substrate effects in Ag–Co nanoalloy systems

“…Van-der-Waals forces are responsible for the adhesion of nanoparticles on semi-infinite substrates to a significant extent 32 . They affect the equilibrium shapes and surface diffusion of the adsorbed particles 33 . The reason for this is their long-range character combined with the infinite extension of the substrate.…”