It is noteworthy that a contribution to the Ti-N bonding is given not only by strongly hybridized orbitals of the middle energy region but also by weakly overlapped deep states which provide about 40% of the Ti-N bond strength. At the same time, the Ti-Ti COHP is negative over the whole occupied region, however the Ti-Ti bond strength is only 0.321 eV, i.e. it is eight times weaker as compared to Ti-N bonding.