2 Wave Diffraction and Reciprocal Lattice Diffraction of
- Slides: 15
2. Wave Diffraction and Reciprocal Lattice • • • Diffraction of Waves by Crystals Scattered Wave Amplitude Brillouin Zones Fourier Analysis of the Basis Quasicrystals
Diffraction Of Waves By Crystals Bragg’s Law Reflectance of each plane is about 10 3 to 10 5.
Monochromator 1. 16 A neutron beam on Ca. F 2 Relative intensities are due to basis. X-ray Diffractometer on Powdered Si
Scattered Wave Amplitude Fourier Analysis → T where → Define then mi integers bi is called the primitive vectors of the reciprocal lattice, and G a reciprocal lattice vector. i, j, k cyclic
Diffraction Conditions Scattering vector Difference in phases between waves scattered at r and O Scattering amplitude
Diffraction condition: From Problem 1: where Diffraction condition can be written as Bragg’s law (G G)
Laue Equations Diffraction condition: → k lies in the intersection of 3 cones about the crystal axes. Ewald construction • White dots are reciprocal lattice points. • Incident k drawn with end at lattice point. • Scattered k obtained by drawing a circle.
Brillouin Zones Brillouin Zone Wigner-Seitz cell of reciprocal lattice. Diffraction condition → → k is on boundary of BZ. Square lattice
Reciprocal Lattice to SC Lattice Primitive lattice vectors: Primitive cell volume: Primitive reciprocal lattice vectors: Reciprocal lattice is also SC.
Reciprocal Lattice to BCC Lattice Primitive lattice vectors: Primitive cell volume: Primitive reciprocal lattice vectors: Reciprocal lattice is FCC. Reciprocal lattice vector: Cartesian coord 1 st BZ bcc rhombic dodecahedron
Reciprocal Lattice to FCC Lattice Primitive lattice vectors: Primitive cell volume: Primitive reciprocal lattice vectors: Reciprocal lattice is BCC. Reciprocal lattice vector: Cartesian coord 1 st BZ fcc
Fourier Analysis of the Basis Scattering amplitude Structure factor For a basis with s atoms atomic form factor
Structure Factor of BCC Lattice With respect to the SC lattice, the BCC has a basis of 2 atoms at and → E. g. , metallic Na: no (100), (300), (111), or (221) lines (cancelled by extra plane at half separation)
Structure Factor of FCC Lattice With respect to the SC lattice, the FCC has a basis of 4 atoms at →
Atomic Form Factor For a spherical distribution of electron density For forward scattering, G 0 , so that f Z. For X-ray diffraction, f Z. ( X-ray not sensitive to change in n(r) caused by bonding)
- Bragg's diffraction condition in reciprocal lattice
- Lattice poset
- Reciprocal lattice vector
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- Reciprocal lattice
- Reciprocal space
- Reciprocal tensor
- Reciprocal lattice
- Ewald sphere construction
- Difference between full wave and half wave rectifier
- Difference between transverse wave and longitudinal wave
- Bridge type rectifier circuit
- Earthquake p-wave and s-wave travel time graph
- What do all waves transmit
- Mechanical wave and electromagnetic wave
- Transverse wave and longitudinal wave example