First-Principles Thermodynamics of Hydrogen Absorption in Binary C15 Laves Phases

High Resolution Image Download MS PowerPoint Slide Intermetallic compounds are attractive candidates for hydrogen storage applications. This study investigates the thermodynamics of hydrogen absorption in binary AB 2 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: ZrMo 2 and ZrV 2 . Our calculations show that ZrMo 2 accommodates hydrogen exclusively within A 2 B 2 coordinated tetrahedral sites. In contrast, ZrV 2 accommodates hydrogen over both A 2 B 2 and AB 3 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 ZrV 2 . The occupation of both interstitial site types increases the hydrogen storage capacity of ZrV 2 as compared to ZrMo 2 . 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.