[gmx-users] PRODRG - .itp file

[Anton Feenstra]

Luciane Vieira de Mello wrote:
[...]
> The only thing in the itp file which looks strange is the double entry for
> one of the dihedrals
> 
>    6   5   2   1   1   0.0    1.0 3   0.0    1.0 3 ; DI     C2  O1P    P
> O4P
>    6   5   2   1   1   0.0    3.1 2   0.0    3.1 2 ; DI     C2  O1P    P
> O4P
> 
> However, when I delete either one the distorion is much worse!

These two dihedrals are added together to form the normal O-PO3 
torsion potential. So - yes, it looks strange - but yes, it is right.

> Can anybody help?

You have quite a number of (heavily charged) oxygens in your molecule,
which fall outside the exclusions. Also, both the PO4 group and the CO2
group carry a net -1 charge. It might be that these forces cause your
distortion.

-- 
Groetjes,

Anton
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|        | Anton Feenstra                                            |
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