[gmx-users] Ryckaert-Bellemans Dihedral with AMBER

[tarak karmakar]

Dear All,
I need to use one Ryckaert-Bellemans dihedral type of a dihedral in a new
molecule. To do so, I'm including all the coefficients in .rtp file as
given below, (after bonds section)

[dihedrals]
        HX   CX    CX   OX    3  -7.70990 -10.7269 -15.2261 -2.2442
-0.25839 0.0000

The Force field I'm using for the protein is the amber99sb-ildn.ff.
I have  read an old post [
https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-users/2013-April/080306.html]
in the mailing list and got some clues about how to use this kind of
dihedral forms. Accordingly I have approached.

But at the end I've got the following error,
"No default Proper Dih. types"

Do I need to do something more?
Could anyone guide me the proper way of implementing it?


regards,
Tarak