Effect of C atomic concentration on the structural, mechanical, thermodynamic, and electronic properties of Cr–C binary carbides
摘要
Cr–C carbides have important applications in high-temperature fields due to their high melting point and hardness. The current research mainly focuses on the common Cr23C6 and Cr7C3 phases, and there is insufficient research on the other Cr–C binary carbides, especially for the effect of C atomic concentration on the basic physicochemical properties. Here, the structural stability, mechanical, thermodynamic, electronic, and chemical bond characteristics of eight Cr–C binary carbides, including Cr23C6, Cr3C, Cr7C3, Cr3C2, and CrC along with three newly developed Cr2C, Cr4C3, and Cr8C7 structures were systematically investigated by first-principles calculations. The stability of these carbides was confirmed through formation enthalpy, Born stability criterion, and phonon dispersion analysis, with Cr3C2 exhibiting the best stability. The elastic constants and moduli show that Cr–C carbides have high bulk modulus (B > 220 GPa) and shear modulus (G > 110 GPa). Their B/G ratio and Poisson’s ratio reveal the characteristics of both high hardness and good ductility, with the maximum hardness of 17.2 GPa (Cr3C2). In addition, the theoretical fracture toughness and critical energy release rate of such carbides indicating well consist. Electronic structure analysis indicates that the strong Cr-d and C-p orbital hybridization near the Fermi level dominates the metallic conductivity of the material, while population analysis further confirms the covalent metal bond-type mixing characteristics of Cr–C carbides. For the high Debye temperature (