Phase stability, chemical bonding and mechanical properties of titanium nitrides: a first-principles study

Abstract

We have performed first-principles evolutionary searches for stable Ti-N compounds and have found, in addition to the well-known rock-salt TiN, new ground states Ti3N2, Ti4N3, Ti6N5 at atmospheric pressure, and Ti2N and TiN2 at higher pressures. The latter nitrogen-rich structure contains encapsulated N2 dumbbells with a N-N distance of 1.348 Å at 60 GPa. TiN2 is predicted to be mechanically stable and quenchable. Our calculations on the mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness) are in excellent agreement with the available experimental data. Further analyses of the electronic density of states, crystal orbital Hamilton population and the electron localization function reveal that the hardness is enhanced by strengthening directional covalent bonds and disappearance of Ti-Ti metallic bonding.

Investigations on structural, elastic, thermodynamic and electronic properties of TiN, Ti2N and Ti3N2 under high pressure by first-principles

“…Ti 3 N 2 is orthorhombic structure which belongs to space group of Immm. By geometry optimization, the calculated lattice parameters for c-BN, TiN, Ti 2 N and Ti 3 N 2 at 0 GPa and 50 GPa are presented in Table 1 [25,[32][33][34][35], which show that the present optimization and calculations are reliable.…”

“…However, most of their studies focus on the stoichiometric rock-salt TiN, and there are a few studies of non-stoichiometric titanium nitrides. Yu et al [25] made first-principles evolutionary searches for stable Ti-N compound and found, in addition to the well-known rock-salt TiN, new ground states Ti 3 N 2 , Ti 4 N 3 , Ti 6 N 5 at atmospheric pressure, and Ti 2 N and TiN 2 at higher pressure. They also gave the mechanical properties of the Ti-N compounds at 0 GPa.…”

Thermodynamic Routes to Novel Metastable Nitrogen-Rich Nitrides

“…Very recently, titanium pernitride, TiN 2 , was investigated theoretically, 89,90 and was then synthesized under high-pressure synthesis at 73 GPa, with a bulk modulus in the range 360−385 GPa. 70 We calculate the Δμ N 2 for TiN 2 to be +1.18 eV/N, much higher than the precious metal pernitrides.…”

Nonequilibrium ab initio molecular dynamics determination of Ti monovacancy migration rates in B1 TiN

“…Transition-metal (TM) nitride refractory ceramics possess outstanding physical and mechanical properties, including extreme hardness [1][2][3], high toughness [4][5][6], thermal stability [7,8], chemical inertness [9,10], and good electrical conductivity [2,11], which renders them important for a large variety of applications ranging from wear-resistant protective coatings on tools employed in industrial machining [12,13] to diffusion barrier in electronic devices [14,15].…”