Comparison of structural, mechanical and optical properties of tantalum hemicarbide with tantalum monocarbide: ab initio calculations

Abstract

Abstract First-principles calculations are employed to investigate and compare the structural, elastic and optical properties of tantalum hemicarbide Ta2C and tantalum monocarbide TaC. Calculated lattice constants of these carbides are in good agreement with available theoretical and experimental results. The mechanical stability of these carbides is affirmed by the estimated values of elastic constants. The estimated values of Vickers hardness indicate that TaC is harder than Ta2C. The values of Pugh’s ratio and Poisson’s ratio suggest the brittle nature of both Ta2C and TaC. The optical properties of Ta2C along two polarization directions [001] and [100] are studied in details for the first time. Our study shows that the optical properties of both Ta2C and TaC compounds compliment the electronic structure calculations. Optical constants of Ta2C show significant dependence of the state of polarization of the incident electric field, and predict this material as optically anisotropic.