dihedral restraints need more documentation
It seems the documentation of dihedral restraints was done incompletely. There may be some mismatches between the code and the limited documentation in 4.3.3 of the manual (see issue #597). David Mobley reports (http://lists.gromacs.org/pipermail/gmx-users/2011-October/064968.html) that the use of
dihre-fc is not documented in the manual. Inspection of
mdp_opt.html confirms that.
Assigning to Erik, as he made the commit in 2002 that implemented dihre-fc :)