Structural and Mechanical Properties of TiN-TiC-TiO System： First Principle Study

Mechanical and structural properties of ternary system of TiN-TiO-TiC are investigated using first principle methods. 70 different compositions of Tiloo （NOC）loo with cubic structure are examined in order to illustrate the trend of properties variations. The geometry of compounds is optimized, and then, their chemical stability is assessed. Afterward, shear, bulk and young moduli, Cauchy pressure, Zener ratio, hardness and H3 /E2 ratio are computed based on elastic constants. Graphical ternary diagram is used to represent the trend of such properties when the content of nitrogen, oxygen and carbon varies. The results show that incorporation of oxygen into the system decreases the hardness and H3 /E2 ratio while subsequently ductility increases due to positive Cauchy pressure. It is revealed that the maximum H3 / E2 ratio occurs when both nitrogen and carbon with a little amount of oxygen are incorporated. TilooN3oCTo owns the highest hardness and H3/E2 ratio equal to 39.5 and 0.2 GPa, respectively. In addition, the G/B of this compound, which is about 0.9, shows it is brittle. It is also observed that the solid solutions have better mechanical properties with respect to titanium nitride and titanium carbide. The obtained results could be used to enhance monolayer coatings as well as to design multilayers with specific mechanical properties.