arXiv subjects

David Immel

Publications and source records attributed to David Immel.

3 recordsLinked to original sources

arXiv2025

Conservative adaptive-precision interatomic potentials

Adaptive precision molecular dynamics simulations have developed along energy- and force-coupling approaches, which allow for a continuous transition between different particle descriptions or interaction potentials. Most approaches consider different (fixed) spatial regions, which control the transition between the descriptions and consequently avoid a consistent momentum-conserving Hamiltonian description. We present here a new approach to fully integrate the coupling into a Hamiltonian, therefore allowing for a conservative description, which, by design, guarantees both energy and momentum conservation. By coupling a fast EAM potential to a highly accurate ACE potential, we verify numerically the conservation properties and show that one can achieve - dependent on both the potential and the atomistic system - a speedup of one or two orders of magnitude compared to a pure ACE simulation.

physics.comp-ph↗

arXiv2025

Nanoindentation simulations for copper and tungsten with adaptive-precision potentials

We perform nanoindentation simulations for both the prototypical face-centered cubic metal copper and the body-centered cubic metal tungsten with a new adaptive-precision description of interaction potentials including different accuracy and computational costs: We combine both a computationally efficient embedded atom method (EAM) potential and a precise but computationally less efficient machine learning potential based on the atomic cluster expansion (ACE) into an adaptive-precision (AP) potential tailored for the nanoindentation. The numerically expensive ACE potential is employed selectively only in regions of the computational cell where large accuracy is required. The comparison with pure EAM and pure ACE simulations shows that for Cu, all potentials yield similar dislocation morphologies under the indenter with only small quantitative differences. In contrast, markedly different plasticity mechanisms are observed for W in simulations performed with the central-force EAM potential compared to results obtained using the ACE potential which is able to describe accurately the angular character of bonding in W due to its half-filled d-band. All ACE-specific mechanisms are reproduced in the AP nanoindentation simulations, however, with a significant speedup of 20-30 times compared to the pure ACE simulations. Hence, the AP potential overcomes the performance gap between the precise ACE and the fast EAM potential by combining the advantages of both potentials.

cond-mat.mtrl-sci↗

arXiv2024

Adaptive-precision potentials for large-scale atomistic simulations

Large-scale atomistic simulations rely on interatomic potentials providing an efficient representation of atomic energies and forces. Modern machine-learning (ML) potentials provide the most precise representation compared to electronic structure calculations while traditional potentials provide a less precise, but computationally much faster representation and thus allow simulations of larger systems. We present a method to combine a traditional and a ML potential to a multi-resolution description, leading to an adaptive-precision potential with an optimum of performance and precision in large complex atomistic systems. The required precision is determined per atom by a local structure analysis and updated automatically during simulation. We use copper as demonstrator material with an embedded atom model as classical force field and an atomic cluster expansion (ACE) as ML potential, but in principle a broader class of potential combinations can be coupled by this method. The approach is developed for the molecular-dynamics simulator LAMMPS and includes a load-balancer to prevent problems due to the atom dependent force-calculation times, which makes it suitable for large-scale atomistic simulations. The developed adaptive-precision copper potential represents the ACE-forces and -energies with a precision of 10 meV/{\AA} and 0 meV for the precisely calculated atoms in a nanoindentation of 4 million atoms calculated for 100 ps and shows a speedup of 11.3 compared with a full ACE simulation.

physics.comp-ph↗