First-Principles Calculations on Electronic, Optical,\nand Phonon Properties of γ‑Bi<sub>2</sub>MoO<sub>6</sub>

The wide band gap\nγ-Bi<sub>2</sub>MoO<sub>6</sub> (BMO) has\ntremendous potential in emergent solar harvesting applications. Here\nwe present a combined experimental–first-principles density\nfunctional theory (DFT) approach to probe physical properties relevant\nto the light sensitivity of BMO like dynamic and structural stability,\nRaman and infrared absorption modes, value and nature of band gap\n(i.e., direct or indirect), dielectric constant, and optical absorption,\netc. We solvothermally synthesized wide band gap <i>Pca</i>2<sub>1</sub> phase pure BMO (≳3 eV) for two different pH\nvalues of 7 and 9. The structural parameters were correlated with\nthe stability of BMO derived from elastic tensor simulations. The\ndesired dynamical stability at <i>T</i> = 0 K was established\nfrom the phonon vibrational band structure using a finite difference-based\nsupercell approach. The DFT-based Raman modes and phonon density of\nstates (DOS) reliably reproduced the experimental Raman and infrared\nabsorption. The electronic DOS calculated from Heyd–Scuseria–Ernzerhof\nHSE06 with van der Waals (vdW) and relativistic spin–orbit\ncoupling (SOC) corrections produced a good agreement with the band\ngap obtained from diffuse reflectance spectroscopy (DRS). The optical\nabsorption obtained from the complex dielectric constant for the HSE06+SOC+vdW\npotential closely resembled the DRS-derived absorption of BMO. The\nBMO shows ∼43% photocatalytic efficiency in degrading methylene\nblue dye under 75 min optical illumination. This combined DFT-experimental\napproach may provide a better understanding of the properties of BMO\nrelevant to solar harvesting applications.