The Structures and Properties of Y-Substituted Mg2Ni Alloys and Their Hydrides: A First-Principles Study

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DOI: 10.4236/ajac.2016.71007    4,741 Downloads   6,114 Views  Citations

ABSTRACT

The structures and properties of Y-substituted Mg2Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg2Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg2Ni, Mg2NiH4 and Mg15YNi8H32 are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg2Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg2NiH4. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.

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Li, Y. , Sun, G. and Mi, Y. (2016) The Structures and Properties of Y-Substituted Mg2Ni Alloys and Their Hydrides: A First-Principles Study. American Journal of Analytical Chemistry, 7, 67-74. doi: 10.4236/ajac.2016.71007.
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