As can be seen in Fig. In Fig. Figure , left panel, it is presented the total valence charge density of TiN in the (001) plane, which shows almost spherical shape of the charge distribution that corresponds to strong ionic character of the Ti-N bonds. The charge transfer from the titanium atom to the nitrogen atom calculated using the Bader method 67 amounts 2.12 e. In Ti 0.75 Al 0.25 N (Fig. With increasing the tantalum concentration in the supercell in increments of 25%, a monotonic As can be seen from the average COHP for Ta-N bonds (Fig. (15) Guler, U.; Naik, G. V.; Boltasseva, A.; Shalaev, V. M.; Kildishev, A. V. Performance analysis