Electron collision and periodic crystal

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Discussion Overview

The discussion revolves around the behavior of electrons in periodic crystal structures, specifically addressing the implications of Bloch theory and the nature of diffraction at the borders of Brillouin zones. It explores concepts related to electron scattering, wave functions, and interference effects in solid-state physics.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant references Ashcroft & Mermin, stating that according to Bloch theory, electrons in a perfectly periodic array of ions experience no collisions, raising a question about diffraction at the Brillouin zone borders.
  • Another participant explains that Brillouin zones represent a k-space version of the unit cell and reiterates that perfect crystals do not have electron scattering events.
  • It is noted that Bragg reflections are attributed to interference effects between electron wave functions rather than scattering of electrons.
  • A participant questions the reason for interference of electron wave functions, suggesting it is due to scattering.
  • Another response clarifies that interference is a fundamental property of waves, implying that if wave functions did not interfere, it would contradict their wave nature.

Areas of Agreement / Disagreement

Participants express differing views on the nature of electron interactions in periodic crystals, particularly regarding the role of scattering versus interference in diffraction phenomena. The discussion remains unresolved with multiple competing perspectives on these concepts.

Contextual Notes

There are limitations in the discussion regarding the definitions of scattering and interference, as well as the assumptions underlying the application of Bloch theory to real-world scenarios.

hokhani
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Ashcroft & Mermin, Solid State Physics, page 315:
"According to the Bloch theory, an electron in a perfectly periodic arrays of ions experiences no collision at all".

But how about the electron at the border of Brillouin zone? How does diffraction take place there?
 
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Brillouin zones are just a k-space version of the unit cell. Your book is telling you that perfect crystals don't have electron scattering events.

For a nice discussion see: http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_2/backbone/r2_1_4.html

The conclusion from Ashcroft & Mermin is included. Note that Bragg reflections (diffraction patterns) are a result of interference effects between electron wave functions, not scattering of electrons.
 
UltrafastPED said:
Note that Bragg reflections (diffraction patterns) are a result of interference effects between electron wave functions, not scattering of electrons.
Ok, Thanks. But why do electron wave functions interfere? As far as I know, it is due to scattering.
 
hokhani said:
But why do electron wave functions interfere?

The "wave function" is a representation of the probability amplitude wave ... and interference is a fundamental wave property. If they _didn't_ interfere it would mean that there is no wave.
 

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