[gmx-users] Dihedral Restraints

[Alexander Bujotzek]

The piece of code in dihres.c does it right (at least for the energy I
would say... can't say anything about the force)... but the equation in
the manual is wrong or at least misleading.

>
>
> On 05/03/11, Sai Pooja  <saipooja at gmail.com> wrote:
>> Hi,
>>
>>  
>>
>> In Manual 4.5.3, the potential for dihedral restraints is the following:
>>
>>  
>>
>> Phi* = (Phi - Phi0)MOD 2Pi
>>
>>  
>>
>> Where Phi is the instantaneous dihedral and Phi0 is the reference
>> dihedral. And the MOD2Pi, I assume, ensures a difference <2Pi.
>>
>>  
>>
>> The Potential is: V=0.5*K*(Phi* - Phi0 -deltaPhi)**2          for all
>> Phi*  > deltaPhi and so on ...
>>
>>  
>>
>> I am just confused if this is just a typo? Why are we subtracting Phi0
>> TWICE??
>>
>>
>
> There's an outstanding Redmine issue on this topic -
> http://redmine.gromacs.org/issues/597. Please contribute anything useful.
>
> Mark
> --
> gmx-users mailing list    gmx-users at gromacs.org
> http://lists.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at
> http://www.gromacs.org/Support/Mailing_Lists/Search before posting!
> Please don't post (un)subscribe requests to the list. Use the
> www interface or send it to gmx-users-request at gromacs.org.
> Can't post? Read http://www.gromacs.org/Support/Mailing_Lists