Stability and mechanical properties of high-La content La–Ni phases by first-principles study

Abstract

The structural stability, mechanical properties and Debye temperatures of La-rich La–Ni (LaNi, La2Ni3 and LaNi2) phases were studied by a first-principles method. The formation enthalpy indicates that the La-rich phase is stable. As the La content increases, the enthalpy of formation decreases. The bonding of La–Ni is covalent and metallic. The La-d and Ni-d orbitals contribute mainly at the Fermi level. The mechanical properties indicate that the La-rich La–Ni phases are brittle. La2Ni3 has the most prominent anisotropy. The hardness of LaNi, La2Ni3 and LaNi2 are 37.62 GPa, 41.61 GPa and 65.06 GPa, respectively. Those phases have the potential to form a superhard material. LaNi2 has the highest Debye temperature (232.88 K). LaNi2 is the most stable among these phases.