| With the development and progress of human science and the improvement of people's living standards and ideological awareness,the excessive use of fossil fuels on the adverse effects of the environment and energy depletion and other issues have aroused widespread concern.So,hydrogen is considered as the most promising ideal clean energy in the great industrial era.For a century,the interaction of hydrogen with metal has become an interesting topic,because the metal hydrogen systems have important application value in many ways.For example,metal hydrogen systems can be used for hydrogen storage,thermal storage and energy conversion,hydrogen purification and recovery,and application on batteries.In this paper,we study the mechanical properties,magnetic properties and electrical properties of Ni,Ni4H2 and NiH by the first-principles method based on density functional theory.Firstly,the geometrical structures are given,and the energy changes with the unit cell volumes,theoretical strengthes and bulk elastic moduli are calculated.The results show that the bulk elastic modulus are smaller and smaller with the increasing of the hydrogen composition,on the contrary the theoretical strength are larger and larger with the increasing of the hydrogen composition.Than the magnetic moments are calculated at equilibrium,and the value is 2.489 ?B for transition metal Ni,1.006 ?B for Ni4H2,and zero for NiH,the result indicate that the magnetic moments are gradually decreased with the increasing of the hydrogen composition.Finally,the density of states(DOS)are calculated.The DOS near the Fermi level are mainly due to the contribution of 3d electrons in the structure of fcc Ni,the DOS are mainly contributed by s electrons of H in the range of-8.5 to-6.7 eV,3d electrons of Ni near the Fermi level in NaCl-type cubic structure Ni4H2,and the DOS are mainly contributed by s electrons of H in the range of-12.0 to-6.4 eV,and 3d electrons of Ni near the Fermi level in NaCl-type cubic structure NiH. |
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