First-principles study on the structure and elasticity of LaNi5 and LaNi4.25Al0.75

The structure and elasticity of LaNi5 and related substituted derivatives LaNi4.25Al0.75 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 results for LaNi5 indicate that calculated lattice parameters and elastic constants are in well agreement with the corresponding experimental data. For LaNi4.25Al0.75, Al atoms still prefer to substitute Ni atoms in the 3g sites and tend to disperse in the middle planes, the bulk modulus (122.4 GPa) and the values of the elastic constants C-11 (198.8 GPa), C-12 (84.5 GPa), C-13 (74.9 GPa), C-33 (233.2 GPa), C-44 (67.9 GPa) are worked out for the first time. The ratios of C-11/C-33 and cla increase by 1.9% and 2.5%, respectively, which indicate that the substitutional derivatives LaNi4.25Al0.75 are observed to change less anisotropic than the host alloy. The densities of states and electronic densities are plotted for analysis the variation trend of the elastic moduli in the system with the substitution of Al atoms. (c) 2006 Elsevier B.V. All rights reserved.