Exploring Phonon Characteristics in Few-Layer MXene V₂CT_<i>x</i> through Raman Analysis and First-Principles Calculations: A Strain-Dependent Investigation

In this study, we explore the impact of uniaxial strain on phonon characteristics of V2CTx MXene through a combination of Raman spectroscopy and first-principles calculation. The Raman spectrum of V2CTx MXene reveals in-plane E1g and E2g modes at approximately 283 cm–1 and 407 cm–1, respectively, stemming from the vibration of vanadium atoms. Through the application of mechanical strain, up to 3.9% along the uniaxial direction, noteworthy alterations are observed in the Raman active optical phonon modes of V2CTx MXene. Particularly, the degenerate phonon mode E1g undergoes a split into two sub-bands when the crystal symmetry is disrupted with minimal strain. The resulting sub-bands, denoted as E1g′ parallel to the strain direction and E1g″ perpendicular to the strain direction, display a blue shift in their respective modes under the influence of strain. The first-principles calculations demonstrate the consistent trend of splitting and blue shift in the E1g phonon mode under strain. Additionally, the Grüneisen parameter (γ) and shear deformation potential have been calculated through Raman spectroscopy and the phenomenological method, considering the diatomic chain model. This comprehensive study not only enhances our comprehension of the light–matter interaction in few-layer 2D V2CTx MXene but also provides valuable insights into the potential applications of this material in flexible optoelectronic devices.