Koopmans’ Transfer Integral Calculation: A Comparison between the Hartree-Fock and the Density Functional Results

The prediction of the charge mobility in conjugated organic systems is of great interest in order to evaluate their potential use as active materials in a wide class of devices. In this field, one of the most used approaches for modeling this process is the Marcus theory, where one of the key parameters to be calculated is the intermolecular transfer integral, J. Different methods have been developed for J calculations, based initially on the Hartree-Fock Hamiltonian and more recently on the density functional ones. However, in literature only few works were focused on the reliability of the values of the intermolecular transfer integrals obtained with density functional calculations. Here, by using the energy-splitting-in-dimer approach we discuss the results of a study on the dependence of J on the type of the density functional approach used and compare them with data from Hartree-Fock Hamiltonian. We found that, under the hypothesis of the Koopmans approach, the Hartree-Fock and density functional results can be seen as the upper and lower limits, respectively, of the corresponding experimental value.