Hydrogen atom distribution and hydrogen induced site depopulation for the La2−xMgxNi7-H system

► Alpha- and beta-phase for La2−xMgxNi7-H system have been characterized. ► Five different interstitial sites are occupied by deuterium/hydrogen atoms in the beta-phase. ► One D/H site has been determined in the alpha-phase. ► Deuterium/hydrogen induced site depopulation during phase transformation is observed. ► Ni atoms tend to have tetrahedral-like D/H atom coordination.