https://doi.org/10.1351/goldbook.P04468
A metal-insulator transition in quasi one-dimensional solids that occurs as a result of a band gap opening up at the Fermi energy due to a displacive distortion of the regular array increasing the unit cell length, usually a dimerization; the decrease in electronic energy outweighs the increase in lattice energy. Example: The transition in methylethylmorpholinium tetracyanoquinodimethanide at