Using the pseudopotential plane-wave method based on density functional theory, the geometrical configuration, energetics and electronic structures of MgH₂ hydrogen storage systems with transition metals Ti, V or Nb doping have been calculated. The doping atom of Ti, V or Nb exhibits more notable affinity with hydrogen as compared with Mg atom. The bonding strength of Mg—H is weakened when the doping atom pulls nearby hydrogen atoms toward itself. Due to the doping of Ti, V or Nb, the structural stabilities of MgH₂ systems are decreased and their dehydrogenation properties are improved, as well as, the dehydrogenation abilities of doped systems are increased gradually in order of MgH₂-Ti, MgH₂-V and MgH₂-Nb systems. The clusters of hydrides formed from doping atoms and hydrogen play significant catalytic role in improving the dehydrogenation properties of MgH₂ systems. The micromechanisms of improved properties lie in the narrowing of the energy gap near Fermi energy level, the decreasing of bonding electrons number as well as the weakening of H—Mg interactions in doped systems.

Key words: MgH₂, pseudopotential plane-wave, dehydrogenation property, electronic structure