Structural, Mechanical and Optoelectronic Properties of Y2M2O7 (M = Ti, V and Nb) Pyrochlores: A First Principles Study

The highly precise spin-polarized density functional approach is utilized to study the structural properties, chemical bonding, mechanical and optoelectronic properties of the cubic Y2M2O7 (M = Ti, V and Nb) pyrochlores. The calculated structural parameters and geometries are consistent with experimental results. Electronic charge density explains that the nature of the bond between Y and M is covalent, whereas Ti-O, V-O and Nb-O bonds are ionic. Mechanical properties of these compounds demonstrate that Y2Nb2O7 and Y2V2O7 are ductile, whereas Y2Ti2O7 is brittle in nature. The electronic band structures confirm the semiconducting nature for all the three materials with band gaps 2.8 eV, 0.2 eV, and 0.4 eV for Y2Ti2O7, Y2V2O7 and Y2Nb2O7, respectively. Optical properties are calculated for the optically active compounds, which show that Y2Ti2O7 and Y2V2O7 are highly dielectric materials and are optically active in the visible and infrared regions of the electromagnetic spectrum.