Why Does Bragg Diffraction Occur for Bound Electrons in a Crystal?

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    Bragg Reflection
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Discussion Overview

The discussion centers on the phenomenon of Bragg diffraction, specifically addressing why it occurs for bound electrons in a crystal, contrasting this with the behavior of free particles like electrons or X-rays. The scope includes theoretical considerations and conceptual clarifications regarding wave-particle duality and diffraction mechanisms.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that Bragg diffraction typically occurs for free particles, questioning how it applies to bound electrons in a crystal.
  • Others argue that Bragg diffraction can be understood in terms of wave behavior, suggesting that electron waves interact with the ionic lattice as a diffracting screen.
  • One participant notes that in classical diffraction, the direction of motion for electrons does not align with the wave vector, raising questions about the classical interpretation of electron behavior.
  • Another participant emphasizes that classical physics does not treat electrons as waves, suggesting that this perspective complicates the notion of Bragg diffraction for bound electrons.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of Bragg diffraction to bound electrons, with no consensus reached on whether classical or wave interpretations provide a satisfactory explanation.

Contextual Notes

The discussion highlights potential limitations in understanding the wave-particle duality of electrons and the implications for diffraction, particularly in distinguishing between classical and quantum mechanical perspectives.

hokhani
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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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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.
 
If we consider the diffraction classically, incident waves are in direction of k and reflected waves are in direction of k^\prime and G=k-k^\prime. But for electrons in crystals direction of motion is not direction of wave vector.
 
Last edited:
hokhani said:
If we consider the diffraction classically, incident waves are in direction of k and reflected waves are in direction of k^\prime and G=k-k^\prime. 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.
 

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