Hydrogen in zirconium: Atomistic simulations of diffusion and interaction with defects using a new embedded atom method potential

$α$-$β$ phase transition of zirconium predicted by on-the-fly machine-learned force field

“…Another important quantity for the prediction of phase transition are the elastic properties, which are typically hard to accurately predict [22,24,62]. Although our MLFFs were trained during a heating/cooling MD simulation at a constant zero pressure only (the focus of the present study is on the temperature-induced hcp-bcc phase transition at ambient pressure), it turns out that the fluctuations of the volumes in the TABLE III.…”

Mechanisms of Hydride Nucleation, Growth, Reorientation, and Embrittlement in Zirconium: A Review

“…Accompanied by hydride precipitation, different phases of hydride form. Despite multiple studies on this subject [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], there is still some controversy over the phase transition, stability, and formation preference of different hydride phases. There are four types of Zr hydride: ζ-Zr 2 H (Trigonal), γ-ZrH (FCT, c > a), δ-ZrH 1.5 (FCC), and ε-ZrH 2 (FCT, c < a) [ 18 , 19 ].…”

“…There are four types of Zr hydride: ζ-Zr 2 H (Trigonal), γ-ZrH (FCT, c > a), δ-ZrH 1.5 (FCC), and ε-ZrH 2 (FCT, c < a) [ 18 , 19 ]. Figure 2 displays the Zr-H-phase diagram and the unit cell of the hydrides with the lowest energy state, according to a first-principles calculation [ 19 , 20 , 21 , 22 ]. Hydrogen atoms all tend to occupy the tetrahedral interstitial sites with the lowest binding energy rather than the octahedral sites in solid solutions or after forming hydrides [ 20 , 21 ].…”

“…Figure 2 displays the Zr-H-phase diagram and the unit cell of the hydrides with the lowest energy state, according to a first-principles calculation [ 19 , 20 , 21 , 22 ]. Hydrogen atoms all tend to occupy the tetrahedral interstitial sites with the lowest binding energy rather than the octahedral sites in solid solutions or after forming hydrides [ 20 , 21 ]. The unit cell of ζ-Zr 2 H is composed of two HCP unit cells stacking along the [0001] direction and hydrogen occupying the two bottom layers of tetrahedral interstitial sites [ 18 , 21 ].…”

“…Hydrogen atoms all tend to occupy the tetrahedral interstitial sites with the lowest binding energy rather than the octahedral sites in solid solutions or after forming hydrides [ 20 , 21 ]. The unit cell of ζ-Zr 2 H is composed of two HCP unit cells stacking along the [0001] direction and hydrogen occupying the two bottom layers of tetrahedral interstitial sites [ 18 , 21 ]. Hydrogen occupies different proportions of tetrahedral interstitial sites in FCC or FCT lattices to form γ-ZrH, δ-ZrH 1.5 , and ε-ZrH 2 [ 22 ].…”