Investigation of optical and thermodynamic characteristics of double transition metal YMX (M = Ti and Zr; X = C and N) MXenes

Abstract

This study explores the optical and thermodynamic characteristics of a novel solid solution comprising two different transition metals, YMX (M = Ti and Zr; X = C and N), which belong to the MXenes family. The calculations in this research employ density functional theory (DFT) combined with the pseudopotential technique. From the absorption spectrum, it can be inferred that the YMX MXenes exhibit photon absorption starting from zero photon energy, providing further evidence of the metallic characteristics of the YMX monolayers. Analysis of the results and graphs of L(ω) for YMN MXenes exhibit the strongest electron-photon interaction along the x-axis direction when compared to YMC MXenes, the sharp plasmonic peaks are as follows: YTiN (18.24 eV) > YZrN (17.63 eV) > YTiC (16.40 eV) > YZrC (7.76 eV). Utilizing the GGA + HSE06 method not only leads to a reduction in the absorption coefficient and optical conductivity of 2D YTiX and YZrX MXenes but also enables faster propagation of electromagnetic waves through these materials, particularly in the x-direction. Moreover, irrespective of the approximations used, YMX MXenes exhibit the highest absorption coefficient in the ultraviolet region of the electromagnetic spectrum, making them suitable candidates for use in optoelectronic devices. The progressive rise in entropy as temperature increases serves as robust evidence, affirming the endothermic characteristics exhibited by the studied MXenes. The replacement of carbon with nitrogen results in an increased Debye temperature. By considering the inverse correlation between Debye temperature ${\Theta }_D$ and heat capacity $C_v$, and analyzing the lattice constant of these compounds, it becomes clear that the YMN MXenes exhibit superior hardness in comparison to the YMC MXenes. This finding is particularly evident within the LDA approximation. Due to superior hardness and layered structure with the metallic nature, YMX MXenes present an ideal option for applications in electrical connections and as a protective coating that offers low friction properties. Furthermore, modifying the electronic band gap of 2D MXenes, along with ensuring their structural stability, could greatly enhance the application of these materials in optoelectronic devices.