[gmx-users] ERROR: invalid enum 'xy' for variable pbc, using 'xyz'

[Darrell Koskinen]

Dear GROMACS Gurus,
I am trying to create an infinite sheet of graphene using periodic 
boundary conditions. I created a sheet which fills the entire xy plane 
and thought that all I needed to do was put the line "pbc=xy" into the 
mdp file. However, when I run the simulation, I get the following error:

ERROR: invalid enum 'xy' for variable pbc, using 'xyz'
Next time use one of: 'xyz' 'no' 'full'

This error confuses me since in the manual it clearly states on page 
146, within the Run Parameters and Programs section, that the options 
for pbc are 'xyz', 'no', or 'xy', which is in contradiction to the error 
message.

Can you please resolve this contradiction for me and let me know if 
there is something else I need to do in order to get a simulation 
running with periodic boundary conditions?

Thanks.

Darrell