Stabilization of Shear Planes

Stabilization of Shear Planes.—The development of our ideas on the factors controlling shear-plane stability is aided by a simple schematic illustration of the relationship 

As an alternative to the above description which relates the shear plane to oxygen vacancies, these extended defects may be discussed in terms of metal interstitial 

These alternative descriptions of shear-plane formation will be valuable in our discussion of mechanism in Section 4. In the account now presented of the relative stabilities of shear plane and point defect structures we will assume that vacancies are the predominant point defects. However, the arguments we present could be adapted for metal interstitial defect structures. 

The predominance in non-stoicheiometric compounds of structures based on point defects or defect aggregates indicates that in most compounds Ep the repulsion energy outweighs the defect elimination term. This suggests that in those materials where shear planes form we should look for some special factor which 

The calculations have been performed to date on Ti407 and TijOg, for which detailed structures are available. To test our proposals relating to cation relaxation the following procedure was adopted. Calculations were performed first on the 

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