[gmx-users] Improper dihedral angle: -30 degree or (360-30) degree

[Justin Lemkul]

On 9/10/17 11:26 AM, Mark Abraham wrote:
> Hi,
> 
> Then it probably doesn't matter, because the code will wrap the actual
> angle and the reference angle to be in the same range. Maybe that range is
> different for the different kinds of improper dihedrals.
> 

I'm not so sure that's true.

https://redmine.gromacs.org/issues/2160

Sign seems to matter, but I still maintain that trying to use an improper to 
maintain non-planarity in general is a bit of abuse of the function; if a group 
is to be allowed to deform out of plane, the proper dihedrals should be 
accounting for this behavior.

-Justin

> Mark
> 
> On Sun, Sep 10, 2017 at 3:13 PM Hoa Trinh <trinhlanhoa at gmail.com> wrote:
> 
>> Dear Mark,
>> I read the chapter more than 3 times already, what I found is just "Note
>> that in the input in topology files, angles are
>> given in degrees and force constants in kJ/mol/rad 2 ."
>>
>>
>> *Lan Hoa*
>>
>> 2017-09-10 7:19 GMT-05:00 Mark Abraham <mark.j.abraham at gmail.com>:
>>
>>> Hi,
>>>
>>> Check out the sections in chapter four of the reference manual.
>>>
>>> Mark
>>>
>>> On Sun, 10 Sep 2017 13:36 Hoa Trinh <trinhlanhoa at gmail.com> wrote:
>>>
>>>> Dear Gromacs community,
>>>> I'd like to know what is the range of improper dihedral angle, [0,pi] ,
>>>> [0,2pi] or [-pi, pi] ?  For example, if I have an angle belonging to
>>>> quadrant
>>>> IV, should the angle be -30 or (360-30) or (180-30) degree?
>>>> I appreciate your help.
>>>> Best regards,
>>>> *Lan Hoa*
>>>> --
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-- 
==================================================

Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry

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