Analyzing Diffraction Patterns: Shape Factor

1. Analyzing Diffraction Patterns:Shape Factor Alejandro Zúñiga Departamento de Ingeniería Mecánica, Universidad de Chile July 13, 2006

2. 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

3. 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”

4. Structure Factor Atomic scattering factor Atom position Reciprocal lattice vector (K=g) It tells us how the atoms within a unit cell scatter the electron wave

5. Shape Factor (Williams and Carter, 1996)

6. Structure Factor Shape Factor Position of each unit cell It tells us how all the unit cells scatter the electron wave

7. Relrods

8. (Williams and Carter, 1996)

9. Wedge-shaped specimen (Williams and Carter, 1996)

10. (Williams and Carter, 1996)

11. (Williams and Carter, 1996)