First-principles study of the crystal structures and electronic properties of LaNi4.5M0.5 (M = Al, Mn, Fe, Co)

The structure, stability and electronic properties of the different B-site partial substituted derivatives LaNi4.5M0.5 (M = Al, Mn, Fe, Co) have been investigated by means of the density functional theory using the full-potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The optimized results indicate that all of Al, Mn, Fe, Co atoms prefer to substitute Ni atoms in the 3g sites. Due to the different radius of elements, the cell volume would increase with the doping Ni (3g) atoms. And the sequence of volume is LaNi4.5Al0.5 > LaNi4.5Mn0.5 > LaNi4.5Fe0.5 > LaNi4.5Co0.5 > LaNi5, which is in agreement with the experimental result. The calculated data of formation and cohesive energies indicate that LaNi4.5Mn0.5 has the stablest structure among five alloys. Based on the analysis of the density of states and charge density, the interactions of Mn–Ni, Fe–Ni, Co–Ni atoms are greatly stronger compared to the Ni–Ni interaction, while the interaction of Al–Ni atoms is weakened. Based on the formation energy of hydrogen atom in LaNi4.5M0.5H0.5, the sequence of bounding hydrogen atoms is LaNi4.5Mn0.5 > LaNi4.5Fe0.5 > LaNi4.5Co0.5 > LaNi4.5Al0.5 > LaNi5.