Reading some papers, there is a bit of a curious observation that does not exactly make a lot of sense to me.
In Quantum Chemistry, different methods exist to carry out geometry optimisation and energy calculations. Quantum chemists can have a huge field day arguing which method and basis set to use.
A common type of calculation used for larger (though large is relative to one's computational resources) is density functional theory (DFT) - because it provides good results on a reasonable time scale.
Now here is where it gets weird: Every method has its basis set - basis sets geared towards DFT and basis sets geared towards couple cluster methods. It is generally recommended not to use a correlation consistent (cc) basis set with a DFT method (and I guess conversely, a basis set aimed at DFT should not be used with a coupled cluster method).
Why then would people benchmark methods using seemingly inappropriate basis sets. E.g. a cc basis set with an M06 functional.
(See for example: Edward G. Hohenstein, Samuel T. Chill and C. David Sherrill; J. Chem. Theory Comput. 2008, 4 (12), 1996–2000)