Hi Zuzana,
I'm actually working on the paramaterization of polyethers with the
GROMOS developers. Currently in G53a?, there's no such torsion O-C-C-O
in GROMOS and I don't advice to use any combination of existing
monoethers. I could figure out that they give the wrong free energy of
hydration. I hope to have the parameters ready before the end of the
year. Meanwhile, you can use the recently optimized parameters for
CHARMM (http://dx.doi.org/10.1529/biophysj.108.133025) though they are
all-atom.
Cheers,
Patrick
Zuzana Benkova a écrit :
Dear GROMACS users
I want to run simulations of polyethyleneoxide melt. In literature I
have found united atoms force fields that performed well for this kind
of simulation. For dihedral potential I need to extend the
Ryckaert-Bellemans potential up to the order of six. I have looked at
the mailing list and found some information which give advice to change
the code for this kind of potential. But I could not figure out where to
do this changes and how to do them. I would need some detail to do it. I
do not have experience with something like this.
My second question also concerns PEO. I tried to use GROMOS force field
as well for simulations. I used the parameters from ffG53a5 files. In
ffG53a5bon.itp I am not sure which code of dihedrals sould be used for
C-C-O-C and O-C-C-O and which one for the bond angles. In the case of
bond angle I found type ga_8 as suitable, but it seems me from the
description that it sould be the same for all three bonds in PEO. This
seems to be not OK, since the bending of C-O-C angle is characterized by
larger bending constant.
I would appreciate any help. Thank you in advance
Zuzana.
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Patrick FUCHS
Dynamique des Structures et Interactions des Macromolécules Biologiques
INTS, INSERM UMR-S665, Université Paris Diderot,
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