Insight into structure, elastic anisotropy, and phonon dispersion relations of Mg17Ce2 and Mg41Ce5 alloys

Abstract

Crystal structure, electronic structure, elastic anisotropy, and phonon of P63/mmc-Mg17Ce2 and I4/m-Mg41Ce5 have been thoroughly studied by employing density functional theory (DFT) in conjunction with density functional perturbation theory (DFPT). The relaxed lattice parameters a and c, equilibrium cell volumes V0 agree with the available experimental reports. The individual elastic stiffness constants Cij's were obtained via “energy-strain” and “stress-strain” techniques. We indicate that both P63/mmc-Mg17Ce2 and I4/m-Mg41Ce5 should be stabilized mechanically. Polycrystalline aggregates, brittle or ductile characteristics, Poisson's ratio, Debye temperature and the integration of elastic wave velocities along various crystal orientations were also derived incidentally. The anisotropy of the directional linear compression and Young's modulus of P63/mmc-Mg17Ce2 and I4/m-Mg41Ce5 were evaluated, it means that both P63/mmc-Mg17Ce2 and I4/m-Mg41Ce5 possess a certain degree of elastic anisotropy under equilibrium lattice constants. Particularly, the phonon dispersions, phonon density of states, and InfraRed, Raman and Silent vibrational modes of both systems are reported for the first time. Based on our calculated phonon vibrations, it is also shown that both the P63/mmc structure of Mg17Ce2 and the I4/m structure of Mg41Ce5 should be stabilized dynamically.