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

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 < 110 >/{111} slip, a splitting of saddle point in TiN was observed. For < 112 >/{111} slip, a stable stacking fault at a(0)/3 < 112 > 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 a(0)/6 < 112 > displacement. The energy barrier for the shuffling of nitrogen atoms from one state to another is calculated to be 0.70eV 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.