First-Principles Calculations of Elastic Properties of LaNi_4.75Sn_0.25 Alloys under Pressure

The equilibrium lattice constants, bulk modulus, shear modulus, elastic constants and Debye temperature of LaNi_4.75Sn_0.25 under pressure are calculated using the full-potential linearized augmented plane wave (FP-LAPW) method as well as the quasi-harmonic Debye model. The results at zero pressure are in excellent agreement with the experimental data. The Sn atom is found to occupy the equivalent 3g site (0.5a, 0.75b, 0.5c) in the quadruple cell. The Debye temperature of LaNi_4.75Sn_0.25 is lower than that of LaNi₅. The dependences of bulk modulus on finite temperature and on finite pressure are also investigated. The results show that the bulk modulus B increases monotonously as pressure increases.