  Uranium-based materials are valuable assets in the energy, medical, and
military industries. However, understanding their sensitivity to hydrogen
embrittlement is particularly challenging due to the toxicity of uranium and
computationally expensive nature of the quantum-based methods generally
required to study such processes. In this regard, we have developed a Chebyshev
Interaction Model for Efficient Simulation (ChIMES) model that can be employed
to compute energies and forces of U and UH3 bulk structures with vacancies and
hydrogen interstitials with similar accuracy to Density Functional Theory (DFT)
while yielding linear scaling and orders of magnitude improvement in
computational efficiency. We show that that the bulk structural parameters,
uranium and hydrogen vacancy formation energies, and diffusion barriers
predicted by the ChIMES potential are in strong agreement with the reference
DFT data. We then use ChIMES to conduct molecular dynamics simulations of the
temperature-dependent diffusion of a hydrogen interstitial and determine the
corresponding diffusion activation energy. Our model has particular
significance in studies of actinides and other high-Z materials, where there is
a strong need for computationally efficient methods to bridge length and time
scales between experiments and quantum theory.
