Vibrational dynamics, electronic structure, and influence of pressure on the phase stability of Sr₃WO₆ complex...

Polycrystalline β-Sr₃WO₆ was synthesized via a conventional solid-state reaction. Room-temperature X-ray diffraction confirms that the compound crystallizes in a triclinic structure, with space group P1 (C₁¹). Void analysis reveals a relatively open framework with a 35.03% void fraction, while Hirshfeld surface analysis reveals that interatomic interactions are dominated by Sr···O/O···Sr contacts (49.8%), followed by W···O/O···W contributions (31.9%). First-principles calculations based on Density Functional Theory (DFT) yield Raman and infrared spectra in excellent agreement with experiment. Electronic structure analysis indicates a direct bandgap of 2.85 eV at the Γ point, classifying Sr₃WO₆ as a semiconductor. The high-pressure lattice dynamics were additionally examined by in-situ Raman spectroscopy from 0.2 to 11.0 GPa. Most Raman modes exhibit positive pressure coefficients, indicating progressive lattice stiffening. In the 80-340 cm^-1 range, mode hardening is predominantly linear, consistent with WO₆ octahedral bending, while a subset of modes (A, B, C, J, N) display negative pressure coefficients below 0.9 GPa. Marked discontinuities and intensity enhancements occur near 1.6 GPa, accompanied by the emergence of a new mode (A₁) at ∼2.0 GPa. Additional spectral restructuring appears at 6.3-7.0 GPa, including new Raman features (B₁, A₀) and modifications in the 120-180 cm^-1 region. At higher wavenumbers (340-1000 cm^-1), strong blue shifts associated with W-O stretching is observed, together with the appearance of O₁, Q₁, T₁, and U₁ modes between 3.6 and 8.9 GPa. High wavenumbers modes (Y, W) evolve non-monotonically, exhibiting convolution near 2.0 GPa, resolution above 5.7 GPa, and the formation of DD₁ at ∼7.0 GPa. The emergence, disappearance, and intensity evolution of Raman bands provide compelling evidence for two pressure-induced phase transformations, while confirming the structural robustness of the WO₆ framework and revealing subtle symmetry modifications under elevated pressure. Finally, the structural analysis based on void distribution and Hirshfeld surfaces provides key insights into the pressure-dependent Raman behavior discussed.