[gmx-users] Purpose of repeated improper dihedrals

[Justin Lemkul]

On 8/2/19 2:38 AM, Dawid das wrote:
> Dear All,
>
> Why some of the improper parameters in CHARMM27 FF are repeated with
> the middle atom types in a different order as in, e.g.
>
> HR1     NR1     NR2     CPH2    2       0.0000  4.184
> HR1     NR2     NR1     CPH2    2       0.0000  4.184

These aren't repeated parameters. They are different parameters 
corresponding to different connectivity.

-Justin

> while some are not, e.g.
> HR3     CPH1    NR3     CPH1    2       0.0000  8.368
>
> Best regards,
> Dawid Grabarek

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Justin A. Lemkul, Ph.D.
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