Theoretical Investigation of the Ground-State Properties of DMTTF−CA: A Step toward the Understanding of Charge Transfer Complexes Undergoing the Neutral-to-Ionic Phase Transition

International audience; A detailed theoretical study based on first-principles DFT calculations is reported for the charge transfer complex 2,6-dimethyltetrathiafulvalene-p-chloranil (DMTTF−CA). Charge transfer estimates reveal that no periodic ordering of neutral and ionic layers is obtained in the low-temperature phase of DMTTF−CA. Similarities and differences with other mixed-stack charge transfer complexes are discussed with the help of a topological analysis of the electron density. Our results also show that the most popular model in this field, which is based on the balance between the cost of ionization and the gain in Madelung energy, should be used with great care. These molecules are far from being point charges, and molecular deformation and polarization should not be ignored.