Problem facing execution of pdb2gmx while using GROMACS 2020

GROMACS version: 2020
GROMACS modification: No
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I am using Gromacs 2020 right now and trying to process my pdb file using the pdb2gmx command. I have kept gromos53a6.ff in my working directory containing all the necessary itp and rtp files. While executing the pdb2gmx command without -ff flag, I’m getting the following message/error.

Feature not implemented:
Can only select the first of multiple force field entries with directory name
‘gromos53a6.ff’ in the list. If you want to use the next entry, run pdb2gmx in
a different directory, set GMXLIB to point to the desired force field first,
and/or rename or move the force field directory present in the current working

While I’m using ff flag and executing the command, I’m getting the following error

Program: gmx pdb2gmx, version 2020
Source file: src/gromacs/gmxpreprocess/pdb2top.cpp (line 209)
Function: void choose_ff_impl(const char*, char*, int, char*, int)

Inconsistency in user input:
Could not find force field ‘gromos53a6.ff/’ in current directory, install tree
or GMXLIB path.

I couldn’t figure out the stuff related to GMXLIB and unable to process my pdb file and create a topology file.

I request you to solve my query.

Kind Regards,


Hi Abishek,

using just gromos53a6 without the .ff should help.

Let me know if that solved the issue!