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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 Ti 1− x C x B 2 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 compositionally-averaged atomic and covalent radii. This study provides useful insights for future exploration of AB 2 -type alloys for hydrogen storage applications. • Formation energies of substituted AB2 alloys generally increase with the unit cell volumes of alloys. • Hydrogenation enthalpies of AB2 alloys can be tuned to a wide range by substitution. • Enthalpies of AB2 hydrides increase with increasing average electronegativity and volume change upon hydrogenation. • Enthalpies of AB2 hydrides decrease with increasing average atomic and covalent radii. [ABSTRACT FROM AUTHOR]