Strain and doping effects on the energetics of hydrogen desorption from the MgH2 (001) surface

On the basis of first-principles calculations we have systematically investigated the energetics of hydrogen desorption from the MgH₂ (001) surface. Based on total energy and electronic structure calculations, two modes namely strain and doping of selected dopants (Al, Si, Ti) and the combined effect of both on the dehydrogenation energies (ΔH) of MgH₂ (001) systems have been analyzed. The maximum improvement in ΔH has been obtained with the combined effect of doping and strain. Among all the dopants, Al gives the lowest value of ΔH when the system Al-MgH₂ is subjected to a 7.5% biaxial symmetric strain whereas the Si-MgH₂ systems show the least improvement in ΔH. The doping of Ti on MgH₂ (001) is also very beneficial even without strain. The reduction in ΔH is caused by the charge localization on the metal atoms, destabilization and the weakening of metal-hydrogen bonds.