[gmx-users] Errors about dihidral angle type 9 in free energy perturbation

Jianguo Li ljggmx at yahoo.com.sg
Thu Dec 4 09:00:30 CET 2014

Dear All,
I am trying to use free energy perturbation module of gromacs to do hamiltonian replica exchange using CHARMM27 all-atom force field (with CMAP) - version 2.0

I am using 4.5.4 version of gromacs

according to manual (Table 5.5), it allows to perturb dihedral angles: proper dih. multi,  ftp 9, phi and k are allowed under 'F.E.'

I have edited charmm files( ffbonded.itp and also ffnonbonded.itp) for "state B" parameters.
but when I run simulations, it throws following error (for 23 lines):
ERROR 1 [file topol-edited-charmm.top, line 1453]:
  Cannot automatically perturb a torsion with multiple terms to different
  Please specify perturbed parameters manually for this torsion in your

What is the fix for this?
Why gromacs is not recognising the 'state B' parameters?

I also tried to do this with higher version of gromacs (including latest). It throws the same error.

Thank you very much for your time. 


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