[Pw_forum] Constraints

[m.g.p.krishna at chem.leidenuniv.nl]

Hi Yuva,

If you look at the previous post, you can see a small example script,  
where a CONSTRAINT card is used. Also to use CONSTRAINT card you  
SHOULD use 'damp' rather than 'bfgs'. It is easy to use 'distance'  
constraint.

But I failed to fix the coordination number for selected atoms (using  
'atom_coord' and 'type_coord') as It described in the previous mail.

Moreover some strange things are there, for example
from the previous input, it do a relaxation if you use:

    CONSTRAINTS
    1 0.5
    'atom_coord' 5 1 3.5 0.5


and you will get an ERROR message if you swap the atom index (VERY  
STRANGE): ie.

    CONSTRAINTS
    1 0.5
    'atom_coord' 1 5 3.5 0.5

So someone can help us to give a working/reliable example script on  
'atom_coord' and 'type_coord' constraints. It will be very useful,  
since the default examples dont include this...

otherwise I am going to do a Quantum-Espresso plugin for ASE/CamD just  
for a reliable geometry optimization. :-(

With best regards

Krishna Mohan GP
Center for Superfunctional Materials
POSTECH
Sotuh Korea.