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On the Nucleation of Dislocations at a Crystal Surface
Author(s) -
Beltz G. E.,
Freund L. B.
Publication year - 1993
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221800203
Subject(s) - dislocation , nucleation , saddle , saddle point , radius , physics , classical mechanics , critical resolved shear stress , critical radius , jump , shear (geology) , loop (graph theory) , condensed matter physics , materials science , geometry , thermodynamics , mathematics , quantum mechanics , shear rate , spheres , computer security , astronomy , computer science , viscosity , composite material , combinatorics , mathematical optimization
An exact expression for the elastic energy associated with a semicircular shear dislocation loop emanating from a free surface is derived (within continuum dislocation theory) and compared with an earlier approximation. The energy required to activate a semicircular dislocation loop into its unstable “saddle‐point” configuration is then re‐calculated, based on the modified expression for the self‐energy. It is found that the shear stress necessary to emit the loop, as a function of temperature, is almost 50% less than earlier estimates. The principal drawback to this type of calculation is also discussed, namely, that the critical radius of an incipient dislocation loop is on the order of one atomic spacing, which is too small for a continuum theory to be valid.