Substitutional effect of Ti-based AB₂ hydrogen storage alloys: A density functional theory study

Stability of AB(2) alloy in Laves phases C14 and C15 were studied by first-principle density functional theory simulations. A range of different combinations of B and C elements in the Ti1-xCxB2 alloys were considered. The formation energies of these alloys generally increase with the unit cell volumes of alloys. The volume also affects the stability of the corresponding metal hydride. We find that the formation energies and the hydrogenation enthalpies of AB(2) alloys are likely to be determined by at least three factors: electronegativity, atomic radius and covalent radius. The enthalpies of AB(2) hydrides increase with increasing compositionally-averaged electronegativity and volume change upon hydrogenation. However, the enthalpies of AB(2) hydrides decrease with increasing compositionallyaveraged atomic and covalent radii. This study provides useful insights for future exploration of AB(2)-type alloys for hydrogen storage applications. (c) 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license ( http://creativecommons.org/ licenses/by/4.0/).