A combined first principles and experimental approach to Bi₂WO₆

Here we synthesized Bi₂WO₆ (BWO) using both solid-state reaction (SBWO) and hydrothermal (HBWO-U and HBWO-S) methods. The orthorhombic Pca2₁ phase purity in all samples is confirmed from Rietveld refinement of X-ray diffraction data, Raman spectroscopy, and Fourier transform infrared spectroscopy. The HBWO-U and HBWO-S morphology revealed rectangular, spherical, and rod-like features with an average particle size of 55 nm in field emission scanning electron micrographs. A high-resolution transmission electron micrograph showed spherical-shaped particles in the HBWO-U sample with an average diameter of ∼10 nm. The diffuse reflectance-derived indirect electronic band gaps lie within the 2.79-3.23 eV range. The BWO electronic structure is successfully modeled by Hubbard interaction U_d and U_p corrected Perdew-Burke-Ernzerhof generalized gradient approximation GGA-PBE+U_d+U_p with van der Waals (vdW) force in effect. The optimized (U_d, U_p) values are further justified by tuning the Hartree-Fock (HF) exact-exchange mixing parameter α_HF from 25% in Heyd-Scuseria-Ernzerhof (HSE06) to 20% in the PBE-HF20% functional. Moreover, no inconsistencies were seen in the GGA-PBE+U_d+U_p+vdW simulated crystallographic parameters, and the elastic tensor, phonon, and linear optical properties. Overall, the computationally cheap GGA-PBE+U_d+U_p with vdW force may have successfully probed the physical properties of BWO.