[Pw_forum] Display of forces in a pure scf run

[Axel Kohlmeyer]

On Tue, Dec 6, 2011 at 12:38 PM, Cristian Degli Esposti Boschi <
degliesposti at bo.imm.cnr.it> wrote:

> Dear developers,
>
> I have a very basic question, that I had never realized so far and has
> been asked by a students of mine...
>
> If I set to .TRUE. the logical fields tstress and tprnfor in the
> &CONTROL stanza of the pw.x input during a pure scf calculation,
> how are the forces on the ions calculated? What do the displayed
> values represent if only a scf calculation is performed and
> the ionic coordinates are not allowed to change?
>

since stefano already answered the first part, here an answer
to the second part. the forces and stress reported represent
the instantaneous forces and stress of the given conformation.
no more, no less. they are uniquely defined by the atom positions
and the electronic structure method (and its parameters) and
that is it. no motion needs to be considered.

ciao,
    axel.



>
> Thanks for your time.
>
> --
> Cristian Degli Esposti Boschi
> CNR-IMM, Sezione di Bologna,
> via Gobetti, 101, 40129, Bologna, Italia
> tel. ++39 051 6399152, fax ++39 051 6399216
> degliesposti -AT- bo.imm.cnr.it
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>



-- 
Dr. Axel Kohlmeyer
akohlmey at gmail.com  http://goo.gl/1wk0

College of Science and Technology
Temple University, Philadelphia PA, USA.
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