Posted by Ignacio Fernández Galván on March 14, 2011 at 17:05:06:
In Reply to: Multistate CASPT2 vs Density keyword posted by Marcin Andrzejak on October 07, 2010 at 12:04:33:
: I do not understand this behavior (could anyone explain it briefly?) and moreover, I am unsure of which of the two results are more credible and should be used for further analysis. The off diagonal elements obtained without the DENSITY keyword are smaller and similar to each other, soe they look better. On the other hand, the DENSITY keyword is used to produce the exact first-order density matrix, so shouldn't it in theory lead to more accurate results?
I don't have the answer, but I have observed similar results. Even more drastic. In a different system, with DENSITY I get meaningless results (energies too large, that are printed as asterisks, 1e+150 oscillator strengths in RASSI), without DENSITY everything looks OK at first sight. This was with Molcas 7.4, I haven't tested this with other versions.