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Intermetallic compounds are attractive candidates for hydrogen storage applications. This study investigates the thermodynamics of hydrogen absorption in binary AB2 Laves phases with the C15 crystal structure. First-principles calculations, cluster expansion models, and statistical mechanics simulations are employed to determine the pressure–composition isotherms for two prototypical Laves phases: ZrMo2 and ZrV2. Our calculations show that ZrMo2 accommodates hydrogen exclusively within A2B2 coordinated tetrahedral sites. In contrast, ZrV2 accommodates hydrogen over both A2B2 and AB3 coordinated tetrahedral sites. Finite-temperature simulations reveal that hydrogen atoms can occupy neighboring edge-sharing tetrahedra and are separated by a distance close to the Switendick criterion in ZrV2. The occupation of both interstitial site types increases the hydrogen storage capacity of ZrV2 as compared to ZrMo2. Building on this insight, we perform a high-throughput search of binary C15 Laves phases and identify several promising candidates that can accommodate hydrogen across multiple interstitial sites. The results of this study provide chemical guidelines for tuning the hydrogen storage capacity of intermetallic compounds.
Paetsch et al. (Wed,) studied this question.