Pd取代对Mg_2Ni及其氢化物结构和性能影响的第一性原理研究

First-principles Investigation on the Structures and Properties of Pd-substituted Mg_2Ni Alloys and Their Hydrides

利用基于第一性原理的密度泛函理论,计算了镁基储氢合金Mg2Ni以及Pd取代的合金Mg12Ni6-xPdx(x=1,2,3)及其氢化物H2-Mg12Ni6-xPdx(x=0,1,2,3)的晶体结构和电子结构.结果表明,Pd取代Mg2Ni中的Ni原子,使其晶胞体积有所膨胀.同时,Pd的取代对Mg—Ni和Ni—Ni间的成键作用有所影响,但影响不大.合金吸氢后,晶胞发生较大变形,体积增大,有利于氢在体相内的扩散.Pd对3d位置Ni的取代,使得Pd—H键强度比原有的Ni—H键有所减弱,同时也使邻近的3b位置的Ni—H键减弱,使氢更容易脱出,有利于放氢温度的降低.

The crystal and electronic structures of magnesium-based hydrogen storage alloy Mg2Ni,palladium substituted alloys Mg12Ni6-xPdx（x=1,2,3）,and their hydrides H2-Mg12Ni6-xPdx（x=0,1,2,3） were calculated via first-principles density functional theory.The results show that the sizes of primitive cell of the intermetallic alloys and hydrides are enhanced by the substitution of Ni with Pd.The interactions of Mg-Ni and Ni-Ni are affected by the substitution,but the influence is not so much.There is greater deformation and volume increase of the crystal cell after the alloy hydrogenation,which favor the hydrogen diffusion in the bulk.The substitution of Ni located in 3d with Pd atom leads Pd-H bonding interaction to be weaker than the original Ni-H bond,and also leads to the weakening of the neighboring Ni-H bond located in 3b.So the substitution can make hydrogen release more easily and reduce the dehydrogenation temperature.