[gmx-users] Grompp errors while changing combination rules

Apramita Chand apramita.chand at gmail.com
Tue Jul 17 11:40:18 CEST 2018

Dear All,
I had enquired earlier about the steps for changing combination rules in
GROMOS ff. As I understood from your answers, if I am to take combination
rule 3, I can put  sigma and epsilon for my atomtypes under the C6 and C12
columns in ffnonbonded.itp  and these numbers will be interpreted as sigma
and epsilon when I specify the combination number. Also, I don't need to
add anything in the non-bonded params section as  the interactions will be
automatically calculated. I have specified the 'gen-pairs'=yes in the
defaults section for this purpose. But when I try to minimise the system I
get the message:

Too many warnings (2862), g_grompp terminated.
If you are sure all warnings are harmless, use the -maxwarn option.

WARNING 2862 [file ffnonbonded_modified.itp, line 2927]:
  Too few parameters on line (source file
  /builddir/build/BUILD/gromacs-4.5.7/src/kernel/toppush.c, line 820)

I had taken the exact same system and files with combination rule 1 and the
simulation ran smoothly.

What could be the problem? Is there anything I have missed out ?Should I
use the maxwarn option?

Your help will be highly appreciated.

Thanking you,
Yours sincerely,
Apramita Chand

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