Unconstrained relaxation of unit cell (cg3) at 600eV compared to 900eV and volume scan at 600eV:

  system           600cg3  900cg3   600vs
anthraquinone       9.443   9.669   9.733
benzene             9.270   9.544   9.575
benzeneF6          12.575  13.261  13.395  * difference is 6%
naphthalene         9.163   9.413   9.449
pentacene           8.968   9.169   9.242
TCNQ               12.184  12.424  12.507
triazine            9.966  10.202  10.227
triphenylbenzene    9.314   9.549   9.597