PC GAMESS-related discussion club

Joseph Flora
flora-joseph@sc.edu

I compared PCGamess and G03W results of a small system with a transition metal and got disturbing results with default settings. I'm using DFT/B3LYP1, SBKJC for the transition metal, and 6-31G(d) for the rest of the atoms. Basis sets were explicitly specified and are identical. I get binding energy differences of 14-15 kcal/mole between PCG and G03W. I've changed nrad in PCG to be equivalent to that of G03W (and vice versa), and no appreciable change in results. LMAX is the same for both defaults. It appears that the main difference is caused by the transition metal. If I compare just the energies (some have said this is not valid because of differences in code - but binding energies should be similar), I get a 2.6 kcal/mol difference for the transition metal alone, 0.6 kcal/mole for the system without the metal, and 16.6 kcal/mol for the system with the metal. Any thoughts on why such large differences and how to reconcile the two?

Thanks.

Joe