[Pw_forum] Constraints

[yuva rani]

Sir with your suggestions I have constrained two pentacene molecules
stacked one above the other using flags. But it did not worked. so
please provide me a detailed definition and syntax for using
constraints.

I also have another doubt, I am constructing a metal-organic
interface.I built an layered structure using matreial studio and the
cartesian coordinates are taken using chemcraft. How should I input
the coordinates in quantum espresso, whether cartesian or fractional
and the also cell parameters of the specified layered structure.

Thanks in advance.

On 6/13/11, m.g.p.krishna at chem.leidenuniv.nl
<m.g.p.krishna at chem.leidenuniv.nl> wrote:
> 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.
>
>
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