First-principles study on hydrogen diffusion behavior at AlCrTaTiZr/AlCrTaTiZrN₅ composite interface

In this work, the special quasi-random structure (SQS) method was employed to construct supercell models of AlCrTaTiZr high-entropy alloy and AlCrTaTiZrN₅ high-entropy nitride. The optimal crystal planes and equilibrium interface spacing were screened based on surface energies and interface separation energies, thereby establishing a stable AlCrTaTiZr/AlCrTaTiZrN₅ composite interface.

The interstitial site occupancy, solution energy, and cross-interface diffusion barrier of hydrogen atoms were systematically investigated using first-principles calculations. The results indicate that hydrogen atoms preferentially occupy octahedral interstitial sites in the nitride ceramic layer, whereas they tend to occupy tetrahedral interstitial sites in the alloy layer. In the interface region, the solution energies of hydrogen are entirely positive, suggesting that hydrogen segregation or retention is thermodynamically unfavorable.