[gmx-users] GROMPP COMMAND

[Andy Chao]

Dear GROMACS Users:

I have a question regarding using the GROMPP command..

I first used the g_x2top command to convert the *.gro file of a graphene
sheet to the *.top file of the graphene sheet by using the forcefield.itp
file in the OPLSAA file folder as the following:

g_x2top -f graphene.gro -ff oplsaa -o graphene.top

and then use the grompp to run energy minimization

grompp -f em.mdp -c graphene.gro -p graphene.top -o NPT.ptr

why do I get error messages as the following:

Program grompp, Version 4.6.5
source code file: /build/buildd/gromacs-4.6.5/src/kernel/topio.c, line: 752

Fatal error:
Syntax error - File forcefield.itp, line 24
Last line read:
'opls_071  CG   6   12.01100   0.00   A 3.500000E-01   2.92880E-01'
Found a second deaults directive.

What I don't understand is, why the same forcefield.itp file that allows
the *.gro file to be converted to the *.top file has problems when we try
to use it to run the grompp file?

How should I fix this problem?

Thanks!

Andy