We now turn to total interaction energies for these large complexes, using 6-31+G(d) to evaluate δE HF . (Although we have large-basis benchmarks for δE HF , this allows us to present timing data for realistic applications using the mixed-basis procedure.) Interaction energies and timing data for DNA-ellipticine are presented in Table 10, using a variety of basis sets for the other energy components besides δE HF .