Dislocations Structure and energetics

13 Thought experiment creating edge (b) and screw dislocations (c) in an ideal crystal (a). The crystal is cut open as far as the indicated line (a) the lower part of the crystal is then moved downwards (b) or to the right (c). 

It should be remembered that such reactions are not equilibrium processes and therefore a spontaneous back reaction need not be considered. On account of the metastability, the nature, number and distribution of the dislocations naturally depend on the sample s history. The number of dislocations ranges between 0 (for not too large crystals of silicon after careful preparation) and values as high as 10 /cm (in the case of heavily worked copper or gold). 

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