Quantum insights into O-terminated transition metal carbides: Structural and functional perspective for energy solutions

Abstract

The class of two-dimensional MXenes, specifically transition metal carbides like X${}_2$CO${}_2$ (X = Zr, Hf, Nb, Ta), shows significant potential for optoelectronic and thermoelectric applications. This study uses density functional theory (DFT) within the Wien2K code, with the Perdew–Burke–Ernzerhof (PBE) functional, to explore the structural and optical properties of these MXenes. Phonon dispersion calculations confirm the dynamical and thermal stability of the compounds, while detailed anisotropic analysis reveals significant in-plane and out-of-plane variations in optical and electronic behavior. All X${}_2$CO${}_2$ compounds demonstrate hexagonal symmetry (space group: 194) and indirect band gaps, promising for photovoltaics and photodetectors. Optical evaluations cover the dielectric function, refractive index, extinction coefficient, absorption, reflectivity, and Surface Energy Loss Function (SELF) and Volume Energy Loss Function (VELF) analysis to characterize plasmonic behavior. Additionally, BoltzTraP models thermoelectric behavior, identifying temperature-dependent trends in thermal and electrical conductivities, the Seebeck coefficient, and the figure of merit (ZT). These results offer a comprehensive view of X${}_2$CO${}_2$ MXenes, underscoring their potential in next-generation optoelectronic and thermoelectric applications.