First principles calculations of (La,Mg)2Ni7 hydrides

•We perform a systematic DFT by distributing H atoms into 13 interstitial sites of 3 A2Ni7 host compounds.•It is demonstrate that H goes in [A2B4A2B4] slab in La2Ni7 compound.•For Mg-substituted, H goes in both [A2B4A2B4] and [AB5AB5] slab.•The calculated volume and site preferences are in agreement with the experimental data.

Between interstitial metal hydrides, such as LaNi5H6, and ionic complex such as Mg2NiH4, a large family of (La,Mg)–Ni hydrides exists, exhibiting intermediate electronic properties. Using first principles calculations, a systematic investigation of the electronic properties of these (La,Mg)NiyHx hydrides was performed.In the present work, we focus on the calculated preferential H sites. A comparison between geometrical and chemical arguments, leads to a general trend which governs the stability of the hydrides of the (La–Mg)–Ni compound family, namely that the Mg substituted hydrides are less stable. As an example, the (La,Mg)2Ni7Hx hydrides are fully presented. Crystallographic features and possible ordered hydride description are compared with available experimental data.