First-principles Calculations of Phonon and Thermodynamic Properties of Hydrogen Storage α-LaNi₅H

Abstract

The phonon distribution of hydrogen storage α-LaNi 5 H with 4h, 6m, 12n, and 12o interstitial hydrogen was calculated by using first-principles potential surfaces with a 2×2×2 supercell model in order to investigate structural and thermodynamic properties. Frequency shifts due to the phonon contribution from the internal energies of 12n < 6m < 12o < 4h appeared in specific modes originating from interstitial hydrogen and in the upper-edge modes with nickel-lattice motion. The thermodynamic stability of 12n interstitial hydrogen in α-LaNi 5 due to the wide XZ storage space can be explained by its phonon amplitudes and the charge density around nickelbonded hydrogen.