[Pw_forum] CONSTRAINT card

[Vivek Ranjan]

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