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

2014/11/06 by Shuyin Yu, Yu, Shuyin, Qingfeng Zeng +7 · 1 citation
Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #cond-mat.mtrl-sci

paper · pdf · doi:10.48550/arxiv.1411.1485

8 pages, 7 figures

arxiv created 2014/11/06 · arxiv updated 2014/11/07

Abstract

We have performed first-principles evolutionary searches for all stable titanium nitrides and have found, in addition to the well-known rocksalt-type TiN, new ground states Ti₃N₂, Ti₄N₃, Ti₆N₅ at atmospheric pressure, and Ti₂N and TiN₂ at higher pressures. The latest nitrogen-rich structure presents encapsulated N₂ dumbbells with a N-N distance of 1.348 Å at 60 GPa and TiN₂ is predicted to be mechanically stable (quenchable). Our calculations of the mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness) are in excellent agreement with the available experimental data and show that the hardness of titanium nitrides increases with increasing nitrogen content. The hardness of titanium nitrides is enhanced by strengthening directional covalent bonds and disappearance of Ti-Ti metallic bonds. Among the predicted compounds, TiN₂ has the highest hardness of 27.2 GPa.

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