[gmx-users] Dihedral parameters in Gromos53A6OXY+D

Patrick Fuchs patrick.fuchs at univ-paris-diderot.fr
Sat Feb 10 11:50:08 CET 2018

Hi Anjana,
you can add several dihedral functions for the same quadruplet of atoms. 
They will add up when you calculate the potential energy for that dihedral.
As for the 53A6OXY+D, the parameters have been merged recently, together 
with other improvements, into a new set called 2016H66 
(10.1021/acs.jctc.6b00187). You can find the FF files for some liquids 
on the web-page of Philippe Hünenberger 
Alternatively, I also put these parameters on my github web page 
(https://github.com/patrickfuchs/CiEj_2016H66), where there is a copy of 
Philippe's file, as well as the topology for non ionic CiEj surfactants 
(coming from this paper 10.1021/acs.langmuir.7b01348). Since these CiEj 
surfactants have a PEG polar head group, it might be convenient for you 
to start from those. For the time being, those files were tested within 
GROMACS 4 versions, but I plan to add other versions for GROMACS 5 and 
2016 in the near future. I realize it would be convenient to also add 
some PEG topologies there (will try to do that before summer).


Le 10/02/2018 à 11:18, Anjana Jayasinghe a écrit :
> Dear All,
> I am trying to change the parameters for a PEG molecule using OXY+D ( https://pubs.acs.org/doi/abs/10.1021/ct300245h) parameters. When I tried to change the dihedral angles of C-C-O-C and O-C-C-O,  there are three new defined dihedral angles for each mentioned types. But in original 53A6, there is only one dihedral type available for those categories. I'm bit confused with OXY+D dihedral parameters for C-C-O-C and O-C-C-O.
> Appreciate, if anyone can help me.
> Thank you.

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