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

摘要

In the equilibrium immiscible Ru-Pd system, the total energies for five possible structures, i.e., A15, D0_9, D0_(19), L1_2, and L6_0, with a stoichiometry of RuPd_3 were calculated as a function of lattice constants, based on the Vienna Ab Initio Simulation Package (VASP). The calculation results predicted that the D0_(19), L1_2, and L6_0 structures were relatively stable and had similar energies, if the spin polarization effect of the Ru atoms was considered, and that the L1_2 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 Ru_(20)Pd_(80) and its lattice constant determined by diffraction analysis also confirmed the relevance of the ab initio calculations.