Assessment of semiempirical methods for the computation of charge transfer in DNA π-stacks

Using CAS-PT2 and CASSCF charge transfer (CT) energies and electronic couplings as reference data, we assess the performance of several semiempirical methods in the calculation of hole transfer in π-stacks of nucleobases. INDO/S is the most reliable of the methods examined. It provides very good estimates for the key CT parameters. While the MNDO, AM1 and PM3 methods give reasonable CT energies, they fail to provide acceptable values of the coupling matrix elements in the stacks.