TiN belongs to NaCl-type cubic structure with the Ti atom sitting at the 1a (0, 0, 0) site, and the N atom at the 1b (0.5, 0.5, 0.5) position. The calculated equilibrium lattice parameter of titanium nitride, 4.255 Å, agrees well with the experimental value of 4.244 Å. The calculated elastic thought to be responsible for ionic bonding and high strength of titanium nitride while weakly overlapped deep states almost do not contribute to Ti-N bonding. At the same time, the occupied t 2g states near the Fermi level are believed to contribute to metallic bonding.