Virtual Workshop on Hydrogen Effects in Materials
January 28 – 29, Kyushu University, Japan

Atomistic Simulation Activities at Sandia
Hydrogen Materials Consortium (H-Mat)
X. W. Zhou1, C. Nowak1, R. S. Skelton1, M. E. Foster1, C. D. Spataru1,Kevin Chu2, R. B. Sills3, J. A. Ronevich1, and C. San Marchi1
1

Sandia National Laboratories, Livermore, California 94550, USA
2
Georgia Institute of Technology, Atlanta, GA 30332, USA
3
Rutgers University, Piscataway, NJ 08854, USA

ABSTRACT- This presentation gives an overview of atomistic simulation efforts atSandia within the Hydrogen Materials Compatibility consortium (H-Mat). We have been
studying three types of structural materials for transportation hydrogen energy
applications including low-cost Fe-C ferritic steels, austenitic stainless steels, andaluminum alloys. For Fe-C, we have constructed a Fe-C-H bond order potential that
captures both ferrite-austenite-martensite transformations and the cementite structure withthe correct interactions with hydrogen. These properties are essential for defining themicrostructure of Fe-C steels but are challenging to capture by interatomic potentials. We
then use this potential in molecular dynamics and Monte Carlo simulations to studyhydrogen populations in various microstructures and hydrogen effects on decohesionenergies of various interfaces. For austenitic stainless steels, we have developed an Fe-NiCr-H quaternary embedded atom method potential that captures trends of ferrite-austenite
stability, stacking fault energies, and H-metal interaction energies. This advances the field
because no quaternary potentials currently exist in the literature and previous Fe-Ni-Cr
ternary potentials in the literature do not ensure stable austenite structures. We have used
the potential to study dislocation mobility laws in stainless steels, hydrogen effects on
stacking fault energy, and slip band intersection mechanisms. For aluminum alloys, wehave developed an Al-Cu-H ternary bond order potential that captures aluminum stacking
fault energy, and Al2Cu compound and H2 gas phases. This also advances the field as noternary potentials exist in the literature and no binary Al-Cu potentials in the literature
capture the Al2Cu compound phases effectively. We also demonstrated that timeaveraged molecular dynamics can be used to calculate converged hydrogen Cottrell
atmosphere around dislocations. This is significant as Cottrell atmosphere formation has
never been studied in detail before with full atomistic resolution, enabling direct
evaluation of theoretical predictions of atmosphere strengthening and solute drag. Many
results of our simulations have begun to reveal phenomena seen in experiments. We will
discuss details on how these results may help explain experimental observations.
Acknowledgement- Sandia National Laboratories is a multi-mission laboratory managed

and operated by National Technology and Engineering Solutions of Sandia, LLC., awholly owned subsidiary of Honeywell International, Inc., for the U.S. Department ofEnergy’s National Nuclear Security Administration under contract DE-NA-0003525. The
authors gratefully acknowledge research support from the U.S. Department of Energy,
Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell
Technologies Office.