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

Shuyin Yu (1) , Qingfeng Zeng (1) , Artem R. Oganov (2, 3, 1) , Gilles Frapper (4) , Litong Zhang (1)

1 School of Materials Science and Engineering
2 MIPT - Moscow Institute of Physics and Technology [Moscow]
3 SUNY - State University of New York
4 IC2MP [Poitiers] - Institut de chimie des milieux et matériaux de Poitiers [UMR 7285]

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 N-2 dumbbells with a N-N distance of 1.348 angstrom 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.

Mots clés: crystal structure prediction; Ti-N system; electronic properties; hardness

Domaines: Chimie théorique et/ou physique; Chimie inorganique

Shuyin Yu, Qingfeng Zeng, Artem R. Oganov, Gilles Frapper, Litong Zhang. Phase stability, chemical bonding and mechanical properties of titanium nitrides: a first-principles study. Physical Chemistry Chemical Physics, 2015, 17 (17), pp.11763-11769. ⟨10.1039/c5cp00156k⟩. ⟨hal-01368462⟩