Peierls distortion

https://doi.org/10.1351/goldbook.PT07442
Distortion of a regular one-dimensional structure with a partially occupied band to give bond alternation, eventually leading to dimerization or oligomerization. The degree of oligomerization, λ depends on the electronic population of the conduction band indicated by the wave vector of the Fermi level kF \[\lambda = 2\ \pi /k_{\mathrm{F}}\]
Note:
A Peierls distortion opens a gap at the @F02341@, producing a net stabilization of the distorted structure. The Peierls distortion for chain compounds is analogous to the @J03361@ for molecules. The prototypical example of the Peierls distortion in organic chemistry is the bond alternation present in polyvinylene.
PT07442.png
Source:
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 381 (https://doi.org/10.1351/pac200779030293)