Structural stability and anomalous compressibility of isoelectronic compounds- URh3 and UIr3

Abstract

The compound was synthesized using arc-melting technique and high-pressure X-ray diffraction studies were carried out up to 25 GPa. It is found to remain in its parent AuCu3 type structure up to the highest pressure studied. Birch-Murnaghan equation of state fit of pressure-volume data gives the bulk modulus to be 262 GPa while the bulk modulus of the similar isoelectronic compound – URh3 is 133 GPa. Rh and Ir being isoelectronic transition metals, their compounds with uranium metal show a dramatic change in the compressibility of the material. First principle computations indicate a significantly large contribution of 5-f electrons of uranium in UIr3. A strong f-d hybridization in UIr3, as compared to URh3, results in high bulk modulus values of UIr3. The high structural stability of UIr3 is also predicted from the density of state plots as compared to URh3. Computed elastic constants of UIr3 indicate the mechanical stability of the lattice.