[gmx-users] charmm27 in gromacs

Tom dnaafm at gmail.com
Wed Feb 15 04:32:37 CET 2012

Dear Gmx Developer or Users,

Can anyone explain which section is for  the parameters of improper
dihedral angle
on the file of ffbonded.itp ?

On the file of ffbonded.itp, there is not any comment to differentiate the
proper and improper
dihedral angle.

E.g. on thie file of ffbonded.itp in the directory of charmm27.ff
There are two sections about dihedral angle:

[ dihedraltypes ]
; i     j       k       l       func    phi0    cp      mult
C       CT1     NH1     C      * 9*       180.00  0.8368  1

[ dihedraltypes ]
; i     j       k       l       func    q0      cq
CPB     CPA     NPH     CPA    * 2*       0.0000  174.0544
There is also no explaination the explaination about the function type 2.

It seems difficult for users to edit the parameters.
Thanks for the explainations!
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