Vibrational Mode Evolution in WSe2 under Pressure: Thermodynamic Insights from Grüneisen Parameters

In this work, we investigate the evolution of the Raman-active modes of bulk WSe 2 under hydrostatic compression up to 8 GPa. The in-plane E 2 g 1 and out-of-plane A 1 g modes both exhibit linear shifts with pressure, from ∼253 cm -1 to ∼265 cm -1 and from ∼258 cm -1 to ∼271 cm -1 , respectively, highlighting the responses of intra- and interlayer bonds to compression. Analysis of these spectroscopic shifts yields mode-specific Grüneisen parameters of γ(E 2 g 1 ) = 0.51 ± 0.02 and γ(A 1 g) = 0.53 ± 0.02, providing a mode-weighted average ⟨γ⟩ = 0.524 ± 0.015, in close agreement with the estimated thermodynamic Grüneisen parameter γth = 0.65 ± 0.02. Using ⟨γ⟩ and previously reported bulk and shear moduli of WSe 2 at ambient pressure, its thermal-shock resistance was estimated to be in the range of typical semiconductors and highly covalent thermal-shock-resistant ceramics. Our results provide quantitative insight into the vibrational behavior of WSe 2 under high pressure. • Systematic high-pressure study of E 2 g 1 and A 1 g phonon modes in bulk WSe 2 up to 8 GPa • Linear frequency shifts reveal anisotropic lattice response and bond-specific stiffening • Determination of mode-specific Grüneisen parameters γ(E 2 g 1 ) = 0.51 and γ(A 1 g) = 0.53 • Mode-weighted Grüneisen parameter determined in agreement with thermodynamic estimates • Estimated thermal-shock resistance positions WSe 2 between typical semiconductors and covalent ceramics