The stability, mechanical properties, electronic structures and thermodynamic properties of (Ti, Nb)C compounds by first-principles calculations

First principles was carried out studying the properties of (Ti, Nb)C compounds based on density functional theory. The integration of mechanical behavior, electronic structures, and thermodynamic properties can be optimized by mediating the concentration of the titanium alloying element. The results revealed that these transition metal compounds were stable with the negative formation energy. Nb0.5Ti0.5C (29.15 GPa) demonstrated the largest hardness characterized by moduli (B, G) because of the stable shell configuration. NbC exhibited the strongest anisotropy from the universal anisotropic index (A(U)) and three-dimensional surface contours. TixNb1-xC compounds displayed relatively strong stress responses along the [001], [110], and [111] directions. Due to the weakening p-d bonding, the ideal tensile strength gradually decreased with the increasing titanium concentration. The electronic structures revealed that the bonding characteristics of the (Ti, Nb)C compounds were a mixture of metallic and covalent bonds. On the other hand, NbC and TiC exhibited a minimum (740.55 K) and maximum (919.29 K) Debye temperature, indicating the stronger metalic bonds of NbC and covalent bonds of TiC.