First principles study on structural, vibrational, electronic and elastic properties of 2D alkaline-earth carbides as a metallic material

Abstract

A detailed first principle investigation of two-dimensional alkaline-earth carbides (M2C; M = Mg, Ca, Sr, Ba) materials is reported for the first time. The M2C structure has been thoroughly investigated using the projector augmented wave (PAW) method under the generalized gradient approximation (GGA) framework of density functional theory (DFT). The M2C compounds are found to be dynamically and energetically stable, according to phonon dispersion studies. The electronic properties of M2C materials provided the essence of band structure and projected density of states of these compounds. Under the investigation of Perdew–Burke–Ernzerhof (PBE) functional, M2C compounds are found to exhibit metallic behavior. In the series of M2C compounds, with an exception of Ba2C compound, remaining appears to be narrow gap semiconducting materials under Heyd-Scuseria-Ernzerhof (HSE06) functional study. Mg2C compund shows the highest work function in the series as 4.47 eV. In addition to the phonon dispersion analysis, we have evaluated their mechanical stability in terms of elastic properties, and the resulting elastic parameters and polar diagrams of Young's modulus and Poisson's ratio validate their mechanical stability. The good metallicity and hardness of 2D M2C compounds might suggest their potential applications as hard conductors.