Classification of Defects 0 Dimensional Defects 2 Dimensional - - PowerPoint PPT Presentation

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Classification of Defects 0 Dimensional Defects 2 Dimensional - - PowerPoint PPT Presentation

Jan 10, 2023 636 likes •806 views

31/10/2019 Crystal Defect 1. Vector repositioned (if necessary) to pass through origin. 2. Read off projections in terms of unit cell dimensions a 1 , a 2 , a 3 , or c 3. Adjust to smallest integer values 4. Enclose in square brackets, no

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Crystal Defect

  • 1. Vector repositioned (if necessary) to pass

through origin.

  • 2. Read off projections in terms of unit

cell dimensions a1, a2, a3, or c

  • 3. Adjust to smallest integer values
  • 4. Enclose in square brackets, no commas

[uvtw]

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0 – Dimensional Defects

  • Point Defects
  • Vacancy
  • Interstitial
  • Substitution

1 – Dimensional Defects

  • Line Defects
  • Edge Dislocation
  • Screw Dislocation

Classification of Defects

2 – Dimensional Defects

  • Plane Defects
  • Grain Boundary
  • Stacking Faults

3 – Dimensional Defects

  • Extended Defects
  • Pores
  • Cracks

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BURGERS VECTOR

The magnitude and the direction of the displacement are defined by a vector, called the Burgers Vector. In figure (a), starting from the point P , we go up by 6 steps, then move towards right by 5 steps, move down by 6 steps and finally move towards left by 5 steps to reach the starting point P . the Burgers circuit gets closed. When the same operation is performed on the defect crystal (figure (b)) we end up at Q instead of the starting point.

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BURGERS VECTOR So, we have to move an extra step to return to P, in order to close the Burgers circuit. The magnitude and the direction of the step defines the Burgers Vector (BV). BV = = b The Burgers Vector is perpendicular to the edge dislocation line. QP  

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