Electronic Structure, Lattice Dynamics, and Pressure-Induced Phase Transitions in Gd ₂ MoO ₆ : A Combined Theoretical and Experimental Study

This study presents a combined theoretical and experimental investigation into the structural, electronic, and vibrational properties of Gd₂MoO₆. To gain deeper insight into its chemical composition, first-principles calculations were employed, emphasizing energy band analysis. The conduction band minimum is positioned at the high-symmetry Γ-point, while the valence band maximum appears between the Z and Γ-points. These results indicate that Gd₂MoO₆ is a semiconductor exhibiting an indirect band gap of approximately 1.92 eV. Furthermore, lattice dynamics were examined using density functional theory (DFT) to interpret the experimental Raman and infrared spectra. Hirshfeld surface and structural analyses reveal that Gd₂MoO₆ exhibits a hybrid ionic-covalent framework governed by dominant Gd-O/Gd-O and Mo-O/O-Mo bonds. Additionally, pressure-dependent Raman spectroscopy was carried out to explore structural modifications resulting from pressure variations. Based on the spectral changes, two phases' transitions were identified at approximately 3.1-3.3 GPa and 9.5-10 GPa, potentially linked to increased disorder of octahedra induced by pressure effects. The principal component analysis and hierarchical cluster analysis identified two phase transitions at near pressure range of 3.1-3.3 GPa and 9.5-10. GPa, which are in agreement with the pressure-dependent Raman studies.