Proceedings Of The Discussion Meeting On Physics Of Defects

Bulletin of Materials Science

, Volume 10, Issue 1, pp 45-51

First online:

Topological defects in crystals: A density-wave theory

  • M Raj LakshmiAffiliated withDepartment of Physics, Indian Institute of Science
  • , H R Krishna-MurthyAffiliated withDepartment of Physics, Indian Institute of Science
  • , T V RamakrishnanAffiliated withDepartment of Physics, Indian Institute of Science

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A new approach for describing dislocations and other topological defects in crystals, based on the density wave theory of Ramakrishnan and Yussouff is presented. Quantitative calculations are discussed in brief for the order parameter profiles, the atomic configuration and the free energy of a screw dislocation with Burgers vector\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {b} = (a/2, a/2,a/2 )\) in a bcc solid. Our results for the free energy of the dislocation in a crystal of sizeR, when expressed as (λb 2/4π) ln (αR/|b|) whereλ is the shear elastic constant, yield, for example, the valueα ⋍ 1·85 for sodium at its freezing temperature (371°K). The density distribution in the presence of the dislocation shows that the dislocation core has a columnar character. To our knowledge, this study represents the first calculation of dislocation structure, including the core, within the framework of an order parameter theory incorporating thermal effects.


Dislocations core energy and structure topological defects in crystals density wave theory