THEORETICAL-STUDY OF THE CHARGE-TRANSFER IN THE ORGANIC-CRYSTAL OF DIMETHYLQUATERTHIOPHENE AND TETRAFLUORO-TETRACYANOQUINODIMETHANE

The electronic and geometrical structures of the organic charge-transf er crystal of dimethylquaterthiophene (DMQtT) and tetrafluorotetracyan oquinodimethane (TCNQF(4)) are calculated self-consistently from first principles using Car-Parrinello techniques. The calculated electronic charge transfer from the DMQtT molecule to the TCNQF(4) molecule is 0 .46e +/- 0.05e. This charge transfer is accompanied by a structural ch ange in which the DMQtT molecule adopts a more quinoid geometry (compa red to the aromatic structure of the neutral DMQtT molecule) and the T CNQF(4) molecule becomes more aromatic. The electronic structure aroun d the Fermi level is characterized by one-dimensional charge transfer states.