Quantum chemical results as input for solid state calculations: charge transfer states in molecular crystals

The difference I - A between the ionization potential and electron affinity of a molecule is one of the input parameters necessary for calculating the energies of charge transfer states in molecular crystals. In the present p aper, the performance of the DFT methodology with several alternative forms of the exchange-correlation potential is tested in this context. Calculati ons are carried out for polyacenes to select the best potentials and to set up a scheme for correcting systematic errors of the approach, which is sub sequently used to calculate the relevant quantity for sexithiophene and per ylenetetracarboxylic dianhydride (PTCDA). Combined with independent calcula tions of the electrostatic energy of charge pairs in these crystals, the re sults are confronted with CT state energies observed in electro-absorption spectroscopy. (C) 2000 Elsevier Science B.V. All rights reserved.