[Pw_forum] Constraints HOWTO

Jairo Arbey Rodriguez Martinez jarodriguezm at bt.unal.edu.co
Tue Nov 17 15:17:58 CET 2009

Dear Dr. Carlo Sbraccia and users

I am making a constraint that forces an atom to move on a plane
defined by A*x + B*y +C*z = D, where (x,y,z) is the position of the
atom. I have followed the detailed instructions of the manual
"constraints_HOWTO.pdf", but what I made does not work. The atom moves
freely. I attach the two modules read_cards.f90 and
constrains_module.f90 with the new constraint, and I hope to get help.
The code compiles, links and executes well, but the constraint does
not work.

The lines in the input are:
1       0.5D-6
mov_on_plane  1     -6.178444739    2.007498388   0.000000000  0.000000000
Some lines of the output are:
     Waiting for input...
     Reading   1 constraints; tolerance:    0.000000
     1) atom   1 is restricted to move on the plane/line
        -6.17844474    * X +  2.00749839    * Y +  0.00000000    * Z =
...  constr target set (n= 1) =  T
   constr_target on atom  1 =  0.00000000
After that, nothing is mentioned in the output about the constraint.
The scf cycles and the relaxation of the ions seem normal. Thanks in
advance for your help
Jairo Arbey Rodríguez M.
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