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X+C Functional Pairings


Dear all,

I wanted to set up a run using a 100% PBE exchange and 100% PBE correlation functional; that is; an X+C pairing akin to the option available in GAMESS US 2013 (PBE) and Gaussian 09 (PBEPBE).

Question: Since Firefly is vastly superior to the mentioned programs, how can I do this in Firefly? Thanks so much!


Supp. Info: Although the question deals also on "how to generally pair X+C functionals in Firefly", the problem or confusion of not being able to compute 100% CPBE and 100% XPBE with Firefly originates since (1) The DFTTYP=PBE96 or even CPBE in Firefly FF8.0.1.pdf is written as using *also* the "PW91 local correlation" and (2) 21 benchmarks employing Gaussian and Firefly match *perfectly* when calculated with B3LYP but not when calculated with PBEPBE and PBE96, respectively.
For point (1), one might speculate that since CPBE is actually a "gradient correction", it makes sense to think as CPW91 as the left hand side of Eq. 3 in Phys. Rev. Lett. 77, 3867, 1996. However, this is not clear for the non-expert and in view of the many benchmarks done I appreciate the guidance!

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