Stability, electronic, magnetic and pressure effect of half-Heusler alloys CNaCa and SiNaCa: A first-principles study

• Total energies of different atomic arrangements for CNaCa and SiNaCa compounds are shown.
• Stabilities of physical and chemical are estimated.
• Both alloys have a large half-metallic gap up to 0.609 and 0.286 eV for CNaCa and SiNaCa, respectively.
• A transition occur from ferromagnetic to nonmagnetic states under a external pressure.

We investigate the electronic and magnetic properties of CNaCa and SiNaCa by using full-potential local-orbital minimum-basis method. The calculations reveal the both alloys are half-metallic ferromagnets (HMF) with the same magnetic moment of 1.00 μB per formula unit, the magnetic moment mainly originates from the strong spin-polarization of p electrons of C atom and partial involvement of d electrons of Ca atom. Both alloys have a large half-metallic gaps, even up to 0.609 eV for CNaCa, meaning they are stable HMF at room temperature. The robustness of half-metallicity against the lattice constant is also calculated. Finally, lattice constant, magnetic moments, and electronic structure are calculated as a function of external pressure, which implies that the exchange splitting in crystal field gradually disappear and a transition occur from ferromagnetic to nonmagnetic states under a external pressure.