[gmx-users] fatal error with charmm/amber forcefield

Sanku M msanku65 at yahoo.com
Wed Jul 31 23:20:47 CEST 2013

Dear Gromacs users,
  I am using gromacs 4.5.4 .
 Is there any known issue/problem in running hamiltonian replica exchange calculations or FEP  with charm27.ff or amber forcefield  in gromacs4.5.4 ? I tried running an hamiltonian replica exchange using charmm27.ff by interpolating A state and B state but it gives error that dihedral terms with multiple values can not be interpolated..One need to write all A and B states in topol.top manually.
 With opls.ff , it does not have any such problem. It works fine... Is it resolved in gromacs 4.6

This is the series error I am getting when using charmm forcefield or amber forcefield:
WARNING 1197 [file topol_scale.top, line 2353]:
  No default Proper Dih. types for perturbed atoms, using normal values

ERROR 323 [file topol_scale.top, line 2354]:
  Cannot automatically perturb a torsion with multiple terms to different
  Please specify perturbed parameters manually for this torsion in your
Any idea?

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