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

[Mark Abraham]

Darrell Koskinen wrote:
> 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?

pbc=xy is only implemented in GROMACS 4. Are you using an earlier version?

(Hint: it's always best to quote your version when asking for help!)

Mark