Peculiarities of nanotwin structures in Ni$_2$Mn$_{1,5}$In$_{0,5}$ and Ni$_2$Mn$_{1,75}$In$_{0,25}$ Heusler alloys

This article presents the results of calculating the phase stability and structural properties of the twin structures of Ni$_2$Mn$_{1,5}$In$_{0,5}$ and Ni$_2$Mn$_{1,75}$In$_{0,25}$ Heusler alloys. The structures with a random and periodic arrangement of Mn-excess atoms in the In sublattice were considered. It is shown that the compositions of Ni$_2$Mn$_{1,5}$In$_{0,5}$ and Ni$_2$Mn$_{1,75}$In$_{0,25}$, with modulation periods of 2–5 and 3–3, respectively, are stable relative to all twin structures. The distribution of Mn-excess atoms does not affect the structural characteristics of the systems. The nanotwin structures of Ni$_2$Mn$_{1,5}$In$_{0,5}$ and Ni$_2$Mn$_{1,75}$In$_{0,25}$ alloys possess similar crystal lattice parameters. An increase in the stability of the structures with respect to the decomposition into constituent stable components is observed with an increase in the concentration of Mn.