Analyzing Diffraction Patterns: Shape Factor

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Analyzing Diffraction PatternsShape Factor

• Alejandro Zúñiga
• Departamento de Ingeniería Mecánica, Universidad
  de Chile
• July 13, 2006

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Outiline

• Introduction
• Diffracted beam intensity
• Structure factor
• Shape factor
• Shape factor for thin foils and wedge-shaped
  specimens
• Diffraction from particles
• Relating features in the DP to the shape factor
• Examples

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Introduction

• Diffraction patterns are not always composed of
  spots and rings only
• Interesting, and sometimes strange, features also
  appear on the diffraction pattern, and we can
  gather a great deal of information by analyzing
  them
• These features are produced by what is called the
  Shape Factor

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Structure Factor
Atomic scattering factor
Atom position
Reciprocal lattice vector (Kg)
It tells us how the atoms within a unit cell
scatter the electron wave
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Shape Factor
(Williams and Carter, 1996)
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Structure Factor
Shape Factor
Position of each unit cell
It tells us how all the unit cells scatter the
electron wave
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Relrods
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(Williams and Carter, 1996)
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Wedge-shaped specimen
(Williams and Carter, 1996)
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(Williams and Carter, 1996)
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(Williams and Carter, 1996)
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