[gmx-users] error, bug (?) using pbc = no

[Jennifer Rendell]

Dear Fellow Users,
Following a suggestion made by David van der Spoel in a recent gmx-users 
digest, I tried using pbc = no for my peptide which I am trying to 
restrain to a helical conformation.

Grompp gave me three warnings:
1. Can only use nstype=Simple with pbc=no, setting nstype to Simple
2. Tumbling ice-cubes: We are not removing rotation around center of mass 
in a non-periodic system. You should set nstcomm = -1.
3. charge non-zero (not a problem)
and an error:
ERROR: Twin-range neighbour searching (NS) with simple NS algorithm not 
implemented

Does this mean I can't use pbc = no?
Puzzled, Jennifer

I am using gromacs 3.1.4.