Can someone explain peierls distortion/transition to me?

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SUMMARY

Peierls distortion describes the phenomenon in one-dimensional polymers, such as polyacetylene, where a half-filled conduction band leads to the formation of an energy gap when the lattice spacing is altered. Specifically, changing the lattice spacing from 'a' to '2a' results in alternating bond lengths, which opens a band gap and stabilizes the lower energy band. This concept is illustrated through the example of hydrogen atoms forming H2 molecules, where bonding and anti-bonding molecular orbitals create a full band and an empty band, respectively. For further understanding, Peierls' book "Quantum Theory of Solids," particularly chapter 5.3, is recommended for derivations.

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  • Understanding of Peierls distortion in solid-state physics
  • Familiarity with one-dimensional polymers, specifically polyacetylene
  • Knowledge of band theory and molecular orbitals
  • Basic concepts of energy gaps in electronic structures
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  • Study Peierls distortion in greater detail through "Quantum Theory of Solids" by Peierls
  • Explore the implications of bond length alternation in one-dimensional materials
  • Research the concept of energy gaps in relation to degenerate bands
  • Investigate molecular orbital theory and its application to diatomic molecules like H2
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Students and researchers in solid-state physics, materials science, and chemistry, particularly those interested in the electronic properties of one-dimensional polymers and band theory.

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Peierls distortion states that for a 1 dimensional polymer (like polyacyteline) with lattice spacing a they should have a half-filled conduction band, why?

And how does changing the lattice space to 2a cause it to form an energy gap? In my mind it should be the same as the first case...
 
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The point is that in Peierls distortion, the bond length change, getting alternatinly longer and shorter. This opens a band gap and only the lower band will be filled, so you get energetic stabilization. This is especially easy to see for a degenerate band, e.g. think of largely spaced hydrogen atoms. If you pair them up into H2 molecules, you will get a full band of binding MO's and an empy band formed from anti-binding MO's.
 
im still fairly confused... is there a simple derivation somewhere i can follow? i tried looking one up but i can't seem to find anything consistent...
 
Did you check Peierls book "Quantum theory of solids" chapter 5.3?
 

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