New predicted two-dimensional MXenes and their structural, electronic and lattice dynamical properties

Abstract

MXenes, transition metal carbides and nitrides, are a bourgeoning class of two-dimensional (2D) materials due to their tunable electronic and magnetic structures, rich surface chemistry and thermal stability. Here, we perform structural, electronic, vibrational and thermal properties of six transition-metal carbides (Re2C, Tc2C, Mo2C, W2C, Os2C, Ru2C) both 2H and 1T phases by first-principle calculations within density functional theory. Although physical and thermal properties of some pristine MXenes put forward to understanding tunable electronic and magnetic properties, many of 1T-phase and almost never of 2H-phase are not investigated in detailed. Firstly, the atomic structure of six MXenes both 1T and 2H phases are optimized, and their respective dynamical stabilities are discussed. Secondly, electronic band structure calculations reveal that the pristine MXenes are metallic. Finally, phonon calculations of pristine MXenes are computed with the density functional perturbation theory and reported. Raman-active modes are predicted and to assign them to specific atomic motions. Ab-initio molecular dynamic simulations (AIMD) are also performed to check the thermal stability of these MXenes. Our results clearly proved that while 2H-W2C, 2H-Mo2C, 2H-Re2C and 1T-W2C can keep the stabilities at very high temperature (1500 K). The results suggest that these pristine MXenes combining with outstanding properties such as non-magnetic metallic state and high-temperature thermal stability would provide promising candidates for using from energy storage to spintronic applications.