[gmx-users] pdb2gmx Could not find force field, when using -ff commandline parameter

[Keith Callenberg]

Hello gmx-users,

I wrote a script to perform a simulation on my Ubuntu 10.04 machine
running Gromacs 4.0.7. At the beginning of the script I convert the
system from pdb coordinates to gro using pdb2gmx. I am using the
GROMOS 45a3 forcefield, specified by -ff G45a3 and it works great.

pdb2gmx -f na.0.pdb -o na_initial.0.gro -ff G45a3 -water spce

However, when I move the script to a Mac OS X 10.6 machine running
Gromacs 4.5.4, I get the following error:

Fatal error:
Could not find force field 'G45a3' in current directory, install tree,
 or GMXDATA path

The forcefield is definitely on the system and works perfectly if I
don't specify the -ff argument, and instead use the interactive
selection. I even copied the file to the local working directory, put
it in a subdirectory named G45a3.ff (as described in the
documentation) and still got the error.

I also tried modifying the GMXDATA path (it was blank) to the path
that contains ffG45a3.itp in /usr/share. No luck there either.

Anyone have any ideas?

Thanks,

Keith