Strain engineering in molybditene: A theoretical insight into the 2D phase of α-MoO₃

Abstract

This first-principles study explores the structural, thermal, mechanical, electronic, optical, and vibrational properties of molybditene, the 2D phase of α-MoO₃ with P2₁/m symmetry. The structure is stable at near room temperature and meets the Born–Huang mechanical criteria. Molybditene shows anisotropic mechanical properties, with Young’s modulus between 84.33 and 138.48 N/m, and Poisson’s ratio from 0.14 to 0.23. It has an indirect band gap with a valence band maximum at the S point and a conduction band minimum at Γ, varying from 1.75 eV (PBE) to 2.95 eV (HSE06). Light polarized along x shows visible range absorption and a peak around 3.50 eV, while y-polarized light is mainly active in the ultraviolet. Strain engineering shows a significant band gap change under the y-strain, from 1.10 to 2.30 eV, while the gap remains stable under the x-strain. Infrared and Raman spectra identify key vibrational modes at 713.06 cm⁻¹ and 708.39 cm⁻¹ , respectively. Notably, the strain also induces substantial changes in the optical response, including enhanced anisotropy and redshifts in the absorption edge, further expanding the potential of molybditene for applications in flexible electronics, strain-tunable sensors, and polarization-sensitive optoelectronic devices.