Metastable Phase Formation in the Immiscible Ru–Pd System Studied by Ab Initio Calculation and Ion Mixing

Abstract

In the equilibrium immiscible Ru–Pd system, the total energies for five possible structures, i.e., A15, D0₉, D0₁₉, L1₂, and L6₀, with a stoichiometry of RuPd₃ were calculated as a function of lattice constants, based on the Vienna Ab Initio Simulation Package (VASP). The calculation results predicted that the D0₁₉, L1₂, and L6₀ structures were relatively stable and had similar energies, if the spin polarization effect of the Ru atoms was considered, and that the L1₂ structure was the most stable one, if the spin polarization effect was considered to be depressed by the crystal field. Interestingly, in ion mixing experiments, a metastable crystalline Ru–Pd phase of fcc structure was indeed obtained in the Ru–Pd multilayered films with an overall composition of Ru₂₀Pd₈₀ and its lattice constant determined by diffraction analysis also confirmed the relevance of the ab initio calculations.