Electron diffraction study of inter‐ and intrapolytypic phase transitions in transition metal dichalcogenides. II. Shear transformations in TaS₂, TaTe₂, and NbTe₂

The interpolytypic transition from the IT to the 2H modification in the TaS₂ system is shown to be a shear transformation. A transformation mechanism is proposed based on partial dislocation movement along successive glide planes. The same mechanism accounts for the observed simultaneous formation of polytypes other than 2H such as 4H_b. The observations confirm the general aspects of the transformation and also the Burgers‐vector analysis of the “transformation dislocations” gives support to the model. Similar shear processes can be invoked for the formation of the polytypes which give rise to particular superstructures in NbTe₂ and TaTe₂.