Orientational peierls transition in quasi one-dimensional organic solids

A simple model of a stack of planar molecular ions is considered in tight-binding approximation. I show that the modulation of the transfer integral of the extended -electron wave functions of two adjacent molecular ions by a rotational degree of freedom and the softening of the corresponding zone boundary libron qL=z0 leads to an orientational Peierls transition. The possible relevance to the metal-insulator transition in tetrathiafulvalene tetracyanoquinodimethane is stressed. © 1975 The American Physical Society.