[gmx-users] wall problem

[Albert]

Hello:

I am going to simulate a membrane system without wrap at z direction 
(pbc=xy). it claimed that it requires a wall. I try to add the following 
parameters into .mdp file:

pbc          = xy
nwall        = 2
wall-type  = 12-6
cutoff-scheme = Verlet

but it failed with grompp with messages:


-------------------------------------------------------
Program grompp, VERSION 4.6.5
Source code file: /home/albert/gromacs-4.6.5/src/kernel/readir.c, line: 1572

Fatal error:
Expected 2 elements for wall_atomtype, found 0
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors
-------------------------------------------------------


does anybody have any idea what's the problem?

thank you very much.

Albert