[gmx-users] multiple dihedrals of P-O bonds

[Benno Portmann]

Hi,

when creating a topology for ATP the dihedrals for -P-OM- or -OS-P-
dihedrals should be made by two cos(..) functions according the
forcefield definition in Gromos96 forcefield as well as in gromacs
forcefield. The
parameters in ffgmxbon.itp are

...
   OS    P    1     0.000       1.046      3
   OS    P    1     0.000       3.138      2
...

These both entrys should be added for each dihedral in the evaluation.

When creating a .tpr file using grompp the first of these two dihedrals
seems to be overwritten, gmxdump only gives the second dihedral. In
Gromacs Version 3.1.2. grompp overwrites the "multiple"-dihedals
noiseless, in Version 3.1.4. it gives warnings. The same happens with
dihedrals containing "CS"-atomtypes.

Any suggestions what to do?


Benno
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