Bragg reflection at the BZ

In summary, Bragg diffraction occurs for free incident particles such as electrons or X-rays, under special conditions. However, in crystals, the direction of motion for electrons is not the same as the direction of the wave vector, making classical Bragg diffraction impossible.
  • #1
hokhani
483
8
As far as I know, Bragg diffraction happens for incident particles which are free; for example free electrons or X-ray are Bragg-reflected under the special conditions. Why the Bragg diffraction happens for electrons which are not free in a crystal?
 
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  • #2
hokhani said:
As far as I know, Bragg diffraction happens for incident particles which are free; for example free electrons or X-ray are Bragg-reflected under the special conditions. Why the Bragg diffraction happens for electrons which are not free in a crystal?
Bragg diffraction happens for WAVES.
Waves can be of any nature and spread in any medium. Electron wave in ion's lattice is a WAVE with ions as diffracting screen.
 
  • #3
If we consider the diffraction classically, incident waves are in direction of [itex]k[/itex] and reflected waves are in direction of [itex]k^\prime[/itex] and [itex]G=k-k^\prime[/itex]. But for electrons in crystals direction of motion is not direction of wave vector.
 
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  • #4
hokhani said:
If we consider the diffraction classically, incident waves are in direction of [itex]k[/itex] and reflected waves are in direction of [itex]k^\prime[/itex] and [itex]G=k-k^\prime[/itex]. But for electrons in crystals direction of motion is not direction of wave vector.
If we consider the diffraction classically

In classical physics electrons are not WAVES, so you could not bragg diffract electrons.
 

1. What is Bragg reflection at the BZ?

Bragg reflection at the BZ refers to the phenomenon of a periodic crystal lattice structure reflecting x-rays or other electromagnetic radiation at specific angles. This reflection occurs at the Brillouin Zone (BZ), which is a unit cell in reciprocal space that represents all possible wave vectors for a given crystal lattice.

2. How does Bragg reflection at the BZ relate to crystal structure?

Bragg reflection at the BZ is directly related to the periodic arrangement of atoms in a crystal structure. The regular spacing of atoms in the crystal lattice causes x-rays to reflect at specific angles, known as the Bragg angles. This reflection pattern can be used to determine the crystal structure of a material.

3. What is the significance of Bragg reflection at the BZ in materials science?

Bragg reflection at the BZ is a key tool for studying the structure and properties of materials. By analyzing the reflection pattern, scientists can determine the crystal structure, lattice constants, and defects in a material. This information is crucial for understanding the physical and chemical properties of materials and developing new materials with specific properties.

4. How is Bragg reflection at the BZ used in X-ray diffraction experiments?

In X-ray diffraction experiments, a beam of x-rays is directed at a crystal, and the resulting diffraction pattern is analyzed. The diffraction peaks correspond to the Bragg angles, which can be used to determine the crystal structure and orientation of the sample. This technique is widely used in materials science, chemistry, and other fields to study the atomic and molecular structure of materials.

5. Can Bragg reflection at the BZ be observed with other types of radiation?

Yes, Bragg reflection at the BZ can also occur with other types of electromagnetic radiation, such as electrons, neutrons, and photons. Each type of radiation has a different wavelength and energy, so the specific Bragg angles will vary. This allows scientists to study different aspects of a material's structure and properties using different types of radiation.

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