paper

Machine Learning Potentials for Hydrogen Absorption in TiCr $_{2}$ Laves Phases

arXiv:2503.22824 · doi:10.1016/j.actamat.2025.121319

Abstract

The energetics of hydrogen absorption in C15 cubic and C14 hexagonal TiCr $_{2}$ H $_{x}$ Laves phases is investigated for $0 < x \leq 6$ with density functional theory (DFT) and machine learning interatomic potentials (MLIPs). The MLIPs are trained with configurations generated through a series of active-learning schemes. Basin-hopping Monte Carlo (BHMC) simulations based on the MLIPs predict minimum-energy hydrogen configurations, along with enthalpies of formation and hydrogen orderings. The obtained phase transformations at 0 K agree well with the experiments at low temperatures. The hydrogen solubility limits in the low-concentration $I^\pm$ phases at 0 K are predicted to be $x = 1.0$ and $x = 1.5$ for the C15 and the C14 phases, respectively. At these concentrations, C15 TiCr $_{2}$ H shows the $C c$ monoclinic symmetry, while C14 TiCr $_{2}$ H $_{1.5}$ shows the $A ma 2$ orthorhombic symmetry, both of which have not been reported for this system. The first and the second hydride phases, i.e., $I^^{2}$ and $Î²'$, at 0 K are found around $x = 3$ and $x = 4$ , respectively, for both the C15 and the C14 phases. In the second-hydride $Î²'$ phases, C15 TiCr $_{2}$ H $_{4}$ shows the $I 4_{1} / a$ tetragonal symmetry, while C14 TiCr $_{2}$ H $_{4}$ shows the $R 3 ˉ c$ rhombohedral symmetry. Hydrogen repulsion are found to extend to edge-sharing interstices, affecting the hydrogen ordering. Furthermore, the $6 h_{2}$ A $_{2}$ B $_{2}$ interstices are found to be energetically substantially more preferable for C14 TiCr $_{2}$ H $_{x}$ than the other A $_{2}$ B $_{2}$ interstices at low hydrogen concentrations, influencing the hydrogen-occupation trend.

Machine Learning Potentials for Hydrogen Absorption in TiCr2​ Laves Phases

Abstract

Machine Learning Potentials for Hydrogen Absorption in TiCr $_{2}$ Laves Phases