  We have carried out a thorough benchmark of the FDE-ET method for calculating
hole transfer couplings. We have considered 10 exchange-correlation
functionals, 3 non-additive kinetic energy functionals and 3 basis sets.
Overall, we conclude that with a 7% mean relative unsigned error, the PBE
functional coupled with the PW91k non-additive Kinetic energy functional and a
TZP basis set constitutes the most stable, and accurate level of theory for
hole-transfer coupling calculations. The FDE-ET method is found to be an
excellent tool for computing diabatic couplings for hole transfer reactions.
