First principles study on d⁰ half-metallic properties of full-Heusler compounds RbCaX₂ (X=C, N, and O)

A first-principles approach is employed to study the structural, electronic, and magnetic properties of RbCaX₂ (X=C, N, and O) full-Heusler compounds. It is observed that RbCaN₂ and RbCaO₂ are new d⁰ half-metals with an integer magnetic moment of 3 μ_B and 1 μ_B in their ferrimagnetic ground states, respectively, while RbCaC₂ is a common metallic compound. Analysis of the density of states of these compounds indicates that the magnetic moment and furthermore, the half-metallicity primarily originate from the spin-polarization of the p-like states of N and O atoms. The half-metallic (HM) gaps of RbCaN₂ and RbCaO₂ are notably large; thus, the half-metallicity is robust against lattice distortion. Such materials are suitable to be grown on various semiconductor substrates. In addition, for RbCaN₂ and RbCaO₂, four possible terminations of the surface are also calculated.