LaNi_4M(M=Ni、Co、Fe)的晶体和电子结构

Geometry and electronic structure of (M=Ni, Co, Fe)

根据密度泛函理论,采用总体能量-超软赝势平面波技术,分析了LaNi5和20%Ni分别被Co和Fe代换后的晶体结构、总体能量、电子态密度以及Mulliken布居电荷.由理论计算得到的晶体结构参数与实验值符合得比较好.取代后合金的晶体结构变化趋势与取代元素的原子半径变化趋势一致.Co和Fe代换可改变合金的电子结构,降低合金的稳定性.Co-d或Fe-d带的位置及其中的电子数影响合金的稳定性.Co或Fe更倾向于取代3g位,且Co取代比Fe取代稳定.合金生成热的理论计算值与实验值较为接近.

The theoretical calculation of LaNi5 and LaNi4M (M=Co, Fe), in which Ni is substituted by Co and Fe respectively, has been performed by adopting the method of total energy based on the density functional theory. The augmented plane wave function was selected as a basis set in combination with ultra-soft pseudopotential technology. The geometry, total energy, electronic density of states and Mulliken population of alloys were analyzed. The theoretical results of crystal structure parameters accord well with that of the experiments. The change tendency of crystal structure parameters of LaNi4M is agreement with that of radius of substituting atom. The electronic structure is modified and the stability decreases due to the substitution of M-element. The stability of LaNi4M is influenced by the position and the electron number of d-bands near Fermi energy level. The M-element is inclined to substitute for 3g-site Ni and Co-substitution is more stable than Fe-substitution. The theoretical value of formation heat of alloy conforms with the experimental results.