[Pw_forum] CONSTRAINT card

[Gabriele Sclauzero]

Please include the full input file in your post (or at least the relevant fraction of it), 
otherwise it is difficult to understand if you are using correctly this feature of pw.

GS

Vivek Ranjan wrote:
> Hello,
> 
> I am wondering how to use CONSTRAINT card ? I want to keep a dihedral
> angle fixed while letting others relax. The way I do it is the
> following:
> 
> I add the following lines:
> 
> CONSTRAINTS
> 1
> 'torsional_angle'  6 7 8 13      150
> 
> 
> at the end of the input file, hoping the program will keep the
> dihedral angle fixed to 150 degrees.
> 
> However, there is no hint in the output if the above input lines are
> read, and if the program tries to maintain that angle. After several
> steps of atomic relaxation, final relaxed structure is calculated.
> When I check the dihedral angle of the final structure using xcrysden,
> I find that all the dihedral angles are changed and none of them are
> equal to 150 degrees.
> 
> Is there any help ?
> 
> 
> --
> Thank you and Regards,
> 
> Vivek Ranjan
> Physics Department
> NC State University, Raleigh, NC
> 
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> 

-- 


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