Abstract
The substitutional doping of Mn and Ti in Mg2Ni phase has been investigated by first principles density functional theory calculations. The calculation of enthalpy of formation shows that among the four different lattice sites of Mg(6f), Mg(6i), Ni(3b) and Ni(3d) in Mg2Ni unit cell, the most preferable site of substitution of Mn in Mg2Ni lattice has been confirmed to be Mg(6i) lattice site. The most preferable site of Ti substitution in Mg2Ni lattice is Mg(6i) position and the stability of Ti-doped Mg2Ni decreases with the increase of substitution quantity of Ti for Mg.
Highlights
Mg2Ni is considered to be one of the most promising hydrogen storage alloys, because of its lightweight, low cost and high theoretical gravimetric hydrogen storage capacity (3.6 mass%, assuming the formation of Mg2NiH4)
We study the substitutional doping of Mn and Ti in Mg2Ni phase by first principles density functional theory calculations
À0.1816 À0.1515 À0.1543 À0.1170 À0.1194 in Table 2, the calculated enthalpy of formation of Mg2Ni unit cell is À3.2691 eV, which can be transferred into À52.57 kJ/ mol Mg2Ni formula unit
Summary
Mg2Ni is considered to be one of the most promising hydrogen storage alloys, because of its lightweight, low cost and high theoretical gravimetric hydrogen storage capacity (3.6 mass%, assuming the formation of Mg2NiH4). It can absorb and desorb hydrogen at moderate temperatures and pressures. To the best of our knowledge, the studies on which position is the most preferable site for Mn and Ti substitutions among Mg(6f ), Mg(6i), Ni(3b) and Ni(3d) in Mg2Ni lattice are lacked. The preferable sites of substitutions of Mn and Ti in Mg2Ni lattice have been determined by total energy
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