Improving the Accuracy of the Charge Transfer Integrals Obtained by Coupled Cluster Theory, MBPT(2), and TDDFT

Theoretical modeling of the charge transport in organic materials in the diabatic representation requires an accurate evaluation of the charge transfer integrals. In this paper, we show that the coupled cluster and MBPT(2) approaches are the methods of choice for performing the benchmark calculations of this quantity, in contrast to some recently published results. We demonstrate that a proper treatment of the involved ionized states, achieved by applying the continuum-orbital strategy, reduces the error of the transfer integrals by one order of magnitude, which in the case of the CC2 method corresponds to a lowering of the mean relative unsigned error (MRUE) from 39.9 to 3.8%. Moreover, we extend the application of the continuum-orbital strategy to the TDDFT method, and show that it leads to a dramatic improvement of the description of ionized states compared to the conventional TDDFT approach, characterized by lowering of MRUE from 209.0 to 24.5%.