Exploring Phonon Characteristics in Few-Layer MXene\nV<sub>2</sub>CT<sub><i>x</i></sub> through Raman Analysis\nand First-Principles Calculations: A Strain-Dependent Investigation

In\nthis study, we explore the impact of uniaxial strain on phonon\ncharacteristics of V<sub>2</sub>CT<sub><i>x</i></sub> MXene\nthrough a combination of Raman spectroscopy and first-principles calculation.\nThe Raman spectrum of V<sub>2</sub>CT<sub><i>x</i></sub> MXene reveals in-plane E<sub>1g</sub> and E<sub>2g</sub> modes at\napproximately 283 cm<sup>–1</sup> and 407 cm<sup>–1</sup>, respectively, stemming from the vibration of vanadium atoms. Through\nthe application of mechanical strain, up to 3.9% along the uniaxial\ndirection, noteworthy alterations are observed in the Raman active\noptical phonon modes of V<sub>2</sub>CT<sub><i>x</i></sub> MXene. Particularly, the degenerate phonon mode E<sub>1g</sub> undergoes\na split into two sub-bands when the crystal symmetry is disrupted\nwith minimal strain. The resulting sub-bands, denoted as E<sub>1g</sub>′ parallel to the strain direction and E<sub>1g</sub>″\nperpendicular to the strain direction, display a blue shift in their\nrespective modes under the influence of strain. The first-principles\ncalculations demonstrate the consistent trend of splitting and blue\nshift in the E<sub>1g</sub> phonon mode under strain. Additionally,\nthe Grüneisen parameter (γ) and shear deformation potential\nhave been calculated through Raman spectroscopy and the phenomenological\nmethod, considering the diatomic chain model. This comprehensive study\nnot only enhances our comprehension of the light–matter interaction\nin few-layer 2D V<sub>2</sub>CT<sub><i>x</i></sub> MXene\nbut also provides valuable insights into the potential applications\nof this material in flexible optoelectronic devices.