The (11-22) and (-12-16) twinning modes modelled by obliquity correction of a (58deg, a+2b) prototype stretch twin

The {11-22} and {11-26} twinning modes were recently put in evidence by Ostapovets et al. (Phil. Mag, 2017)and interpreted as {101-2}-{101-2} double-twins formed by a simultaneous action of two twinning shears. We propose another interpretation in which the twinning modes result from a one-step mechanism based on the same (58deg, a+2b) prototype stretch twin. . The two twins differ from the prototype twin by their obliquity correction. The results are compared with the classical theory of twinning and with Westlake-Rosenbaum model of {11-22} twinning. An unconventional twinning mode recently discovered in a magnesium single crystal based on the same prototype twin will be the subject of a separate publication.