First principles study of structural, electronic, elastic and magnetic properties of cerium and praseodymium hydrogen system REHx (RE: Ce, Pr and x=2, 3)

The structural, electronic, elastic and magnetic properties of cerium, praseodymium and their hydrides REHx (RE=Ce, Pr and x=2, 3) were investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation package. At zero pressure all the hydrides were stable in the ferromagnetic state. The calculated lattice parameters were in good agreement with the experimental results. The bulk modulus decreased with the increase in the hydrogen content for these hydrides. The electronic structure revealed that di-hydrides were metallic whereas trihydrides were half metallic at zero pressure. A pressure-induced structural phase transition from cubic to hexagonal phase was predicted in these hydrides. The computed elastic constants indicated that these hydrides were mechanically stable at zero pressure. The calculated Debye temperature values were in good agreement with experimental and other theoretical results. A half metallic to metallic transition was also observed in REH3 under high pressure. Ferromagnetism was quenched in these hydrides at high pressures.

Graphical AbstractA structural phase transition from cubic-CaF2 to hexagonal-REB2 phase in di-hydride and from cubic-BiF3 to hexagonal-LaF3 in tri-hydride is predicted. The transition pressures are found to be 52, 4.1, 57 and 4.9 GPa for CeH2, CeH3, PrH2 and PrH3 respectivelyFigure optionsDownload full-size imageDownload as PowerPoint slide