[gmx-users] Issues Using CHARMM22* Force Field with GROMACS 5.1

David Rosenman davidjrosenman at gmail.com
Tue Nov 3 21:34:16 CET 2015


I am trying to use the CHARMM22* force field and TIP3SP water model with

I tried using charmm22star.ff.tgz listed here


However, I get the error:
Fatal error:
Unknown bond_atomtype cn9

upon using grompp with any mdp.

I'm guessing the problem is that the field is no longer compatible with
GROMACS 5.1, since it was posted on the website in 2012. Indeed, I had no
issue working with it using GROMACS 4.6.5 in the past.

However, at the moment, I only have access to GROMACS 5.1, so does anyone
know if an updated version of CHARMM22* exists? And if not, would it be
difficult for me to personally fix the compatibility issue?

Or, perhaps I'm doing something else wrong?

Thanks for your assistance.

Best regards,
David J. Rosenman
Postdoctoral Researcher
University of Delaware

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