• nonstoichiometric ZrC0.6;
  • ordered carbon vacancies;
  • twinning structures;
  • interfacial energy

Twinning structures in ordered nonstoichiometric ZrC0.6 have been investigated experimentally and theoretically. Via transmission electron microscopy and selected area electron diffraction measurements, {111}-specific twins have been observed. Interestingly, two special types of twinning interfaces, i.e. (111)C and (111)Zr interfaces, are recognized to be formed as a result of the presence of ordered carbon vacancies. In contrast to the high stacking fault energy for twinning formation in stoichiometric ZrC, first-principles calculations indicate that the presence of ordered carbon vacancies leads to a great reduction in the twinning interfacial energy, thus favouring the stabilization of twinning structures in the ordered ZrC0.6.