TITLE:
The Structures and Properties of Y-Substituted Mg2Ni Alloys and Their Hydrides: A First-Principles Study
AUTHORS:
Yuanyuan Li, Gaili Sun, Yiming Mi
KEYWORDS:
Mg2Ni Alloys, Y Substitution, Hydrides, First-Principles
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.7 No.1,
January
25,
2016
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.