Electronic band structure, elastic, optical and thermodynamic characteristic of cubic YF3: An ab initio study

Abstract

We have calculated the bond lengths dF3→F5,7,8, dF4→F5,6,8, dF2→F5,7,8, dF1→F6,7,8, dF1→8−Y1,2,3, dF9→Y1,2,3, dF1→8−F9 and single-crystal elastic stiffness constants, Cij and polycrystalline elastic moduli at different pressures by using GGA-PBE, GGA-PBESOL and LDA approach for cubic YF3. Yttrium fluoride is found to be elastically stable in the pressure range 0–40 GPa. Shear modulus, linear compressibility and Poisson's ratio have maximum and minimum values along with different crystallographic directions, which explain their predicted anisotropy. The direct Γ-Γ band gap value 5.082 eV indicates towards the insulating character of YF3. The broad band gap is a sign that this compound should function as an emission center. We predicted the first and second-order pressure coefficients of direct and indirect band gaps using the GGA-PBE, GGA-PBESOL and LDA approaches. The estimated volumetric thermal expansion coefficient, constants volume and constant pressure heat capacities and entropy at zero pressure and 300 K are 1.66 × 105 K−1, 82.56 Jmol−1K−1 and 83.59 mol-1 K−1, respectively. The edge of the optical absorption is located at 48.5 nm which is caused by the V1−C1 transition at the Γ point in the Brillouin zone that corresponds very well to the direct band gap at Γ- Γ.