Structure and energy of planar superstructure defects in X2YZ Heusler alloys

Planar superstructure defects (PSDs) have a great influence on the mechanical and functional properties of ternary Heusler alloys, but a complete analysis of their structure and energy is lacking in the literature. In this work, for Heusler alloys of stoichiometric composition X2YZ, having the L21 superstructure, expressions are given for calculating the sublimation energy and the energy of an arbitrary PSD under the assumption of hard coordination spheres and pair interatomic interactions. It is shown that for a given crystallographic orientation there cannot be more than three PSDs with different energies. An expression is given for finding the planes of occurrence of all possible conservative antiphase boundaries (APBs). It is established that in Heusler alloys there are only conservative and nonconservative APBs and there are no defects such as boundaries of C-domains or inversion APBs. The results obtained are useful for the analysis of slip systems and the configuration of magnetic domain walls of the considered family of alloys. [Display omitted] •Structure and energy of planar superstructure defects in Heusler alloys are analyzed.•Heusler alloys support only conservative and nonconservative antiphase boundaries.•List of crystallographic planes with conservative antiphase boundaries is given.•In each plane no more than three defects with different energy can exist.•Energy of any planar superstructure defect is given in terms of pair potentials.