Acceleration of diffusive molecular dynamics simulations through mean field approximation and subcycling time integration

Atomistic modeling and analysis of hydride phase transformation in palladium nanoparticles

“…For simplicity, but without loss of generality, in our DMD simulations we restrict diffusive transport within one shell of neighbors. The above discrete kinetic law has been validated against the classical lattice random walk model for the long-term dynamics of a single H atom in Pd [37]. It has also been applied to study surface segregation in AuAg alloys [38].…”

MXE: A package for simulating long-term diffusive mass transport phenomena in nanoscale systems

“…Thus, H atoms prefer octahedral sites to be located rather than tetrahedral sites. We only considered the octahedral sites in this simulation, in line with previous studies [48,49,50,51]. During the simulation, the host sites were set to be fully occupied by Pd atoms, the atomic molar fraction was always one, while the interstitial sites were allowed to be fully or partially occupied by H atoms.…”

“…In order to address these challenges, several methodologies have been developed, including hybrid Monte Carlo (MC) techniques [15,16], and phase field approaches [17], that have been successful in simulating segregation of solutes near dislocation cores and defects. Furthermore, coupled diffusive techniques using MD -called diffusive MD (DMD)-have also been recently developed [18,19,20,21,22], which are outstanding for simulating heat and mass transport at the nanoscale for very large time scale. DMD-like techniques have been shown successful in simulating a wide range of diffusive phenomena in atomistic systems, including sintering [18], Hydrogen (H) diffusion in Palladium (Pd) nanoparticles [21], Lithium (Li) diffusion in Silicon (Si) nanowires [22], etc.…”

“…Unfortunately, this is not a trivial task, and previous implementations have been based on specific scripts that modified MD codes [18], or in specific, in-house codes restricted to targeted applications [20,21,22], ultimately hindering widespread usage of such techniques.…”

“…This new approach was inspired on the kinematic mean field theory [25], and is analogous to transport laws used for mass transport in other methods [26,18,22]. The proposed kinematic law for transport is then coupled to a non-equilibrium statistical mechanics formulation for atomic systems [27,28,19], allowing the coupled thermo-chemo-mechanical simulation of heat [29,30,31,32] and mass transport at the nanoscale [20,21,22]. We will refer to the framework (and code) as MXE, short for maximum-entropy principle, which is one of the fundamental pillars of the formulation.…”