Thermodynamic and electronic properties of quaternary hydrides LixNa1−xMgH3

Abstract The thermodynamic and electronic properties of Li x Na 1− x MgH 3 ( x  = 0, 0.25, 0.5 and 0.75) have been investigated using the density functional theory within the generalized-gradient approximation. The obtained cohesive energies indicate that the stability of crystal increases with increasing Li element in Li x Na 1− x MgH 3 . The reaction enthalpies for Li x Na 1− x MgH 3 phases have been investigated along four possible dehydrogenation reaction pathways, and the enthalpy change of two pathways is found to be nearly linearly reduced with increasing the Li substitution level from x  = 0 to x  = 0.75. The electronic densities of states show that with increasing Li substitution at Na sites in NaMgH 3 , the band gaps of the wide-band gap insulators Li x Na 1− x MgH 3 become wider, and the contribution of Li s and p states to the total electronic densities of states become larger while Na s and p states become less. The obtained calculation results suggest that Li substitution in NaMgH 3 may result in a favorable modification for onboard hydrogen storage application.