First-principles density functional theory study of generalized stacking faults in TiN and MgO

Abstract

In this paper, the generalized stacking fault (GSF) energies in different slip planes of TiN and MgO are calculated using highly reliable first-principles density functional theory (DFT) calculations. During DFT calculations, the issue of different ways to calculate the GSF energetics in ceramic materials containing more than one element was addressed and applied. For 〈1 1 0〉/{1 1 1} slip, a splitting of saddle point in TiN was observed. For 〈1 1 2〉/{1 1 1} slip, a stable stacking fault at a₀/3〈1 1 2〉 displacement was formed in TiN. For synchroshear mechanism where the slip was accompanied by a cooperative motion of the interfacial nitrogen atoms within the slip plane, a second stable stacking fault was formed at a₀/6〈1 1 2〉 displacement. The energy barrier for the shuffling of nitrogen atoms from one state to another is calculated to be 0.70 eV per atom. In contrast, such features are absent in MgO. These differences highlight the influence of complex bonding nature (mixed covalent, ionic, and metallic bondings) of TiN, which is substantially different than that in MgO (simple ionic bonding) on GSF shapes.

Keywords:

• DFT
• ceramic
• generalized stacking fault energy
• slip
• bonding

Acknowledgements

This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. SKY and XYL also acknowledge partial support by the Los Alamos National Laboratory (LANL) Directed Research and Development Program. LANL is operated by Los Alamos National Security, LLC, for the National Nuclear Security Administration of the US Department of Energy under Contract No. DE-AC52-06NA25396. The authors acknowledge insightful discussions with Prof. J.P. Hirth.