{111} twinning structure and interfacial energy in nonstoichiometric TiCx with ordered carbon vacancies

• The {111} twinning structure in ordered TiC0.7 has been observed and characterized.
• Ordered carbon vacancies lead to reduction in the energy of twinning boundary.
• The twinning interface is recognized to be {111}Ti type terminating.

Here we report the experimental and theoretical investigations of the {111} twinning structures in nonstoichiometric TiC0.7 with ordered carbon vacancies. Owing to the ordering of carbon vacancies, a cubic Ti2C-type ordered phase is formed in nonstoichiometric TiCx (0.53 ≤ x ≤ 0.81). Via the TEM measurements, the {111}-specific twinning structure with incoherent boundary has been observed in ordered TiC0.7. The first principles calculations indicate that the presence of ordered carbon vacancies leads to reduction in the energy of {111}Ti type twinning interface, thus favoring the formation and stabilization of {111}Ti-specific twinning structure in the ordered TiCx.