Incomplete charge transfer stability of organic donor-acceptor compounds

The conditions required to establish the stability of incomplete charge transfer in the ground state of a 1:1 segregated-stack organic compound have been examined for a system involving finite-transfer integral between nearest-neighbor molecules along the donor and acceptor stacks. Molecular ionization energy, crystalline Madelung energy, as well as band or delocalization energy have been included. The three cases investigated, namely, no correlation between electrons on a stack, strong on-site correlation as well as strong nearest-neighbor correlation suggest that correlation between electrons (holes) on the same stack is important in establishing incomplete charge transfer in an organic compound such as TTF-TCNQ (tetrathiafulvalenium-tetracyanoquinodimethanide). © 1977 The American Physical Society.