[Pw_forum] How to reuse cell geometry for successive straining of a lattice

[Axel Kohlmeyer]

On Wed, Jan 22, 2014 at 9:06 PM, Zimmerman, Jonathan A
<jzimmer at sandia.gov> wrote:
> Hi Pw_forum folks,

hi jon,

> I'm new to Quantum Espresso, but I have checked the archives and I don't
> think this question has been asked (at least not this way). Here goes:
>
> I'd like to perform a series of vc-relax calculations on a crystal lattice
> such that each time I increase the amount of applied strain in a given
> direction (via the CELL_PARAMETERS), from one calculation to the next I
> reuse the other, unconstrained CELL_PARAMETERS and the ATOMIC_POSITIONS.
> This way, my Poisson contraction and non-uniform relaxation of the atoms is
> done gently, rather than restarting each calculation with the same
> 'unrelaxed' ATOMIC_POSITIONS. I'm hoping that a few of you have done
> something similar and have a script or suggestions for carrying-over the
> CELL_PARAMETERS (those I'm not fixing) and ATOMIC_POSITIONS from one
> calculation to the next. If so, please respond.

since nobody else responded to your question here are a few thoughts on that:

what you want to do should be easily doable with a little bit of
scripting. i suggest you have a look at the pwo2xsf.sh script that can
be used to extract coordinates from a QE run into an .xsf file, which
contains coordinates and cell vectors. similarly, there is xsf2pwi.sh,
that would convert a set of .xsf coordinates to a format suitable for
input of pw.x. if you write a little script to process a given input
file template, then you can combine these two scripts with your script
and do the processing as you intend to do.

it might also be possible to combine this.

another, more elaborate, option would be to adopt the new "COUPLE"
interface that allows to interface pw.x in a (superficially) similar
fashion as you know it from LAMMPS. so you could make it run a
repeated relaxation output the final coordinates, modify, and
continue. this code is only available through the svn currently. but
if you want to go this route, please contact me off-list and i'd be
more than happy to collaborate with you to write a little "driver" for
your needs.

best regards from philly,

    axel.

>
> Thanks!
>
> Jon Zimmerman
> ----------------------------------
> Jonathan A. Zimmerman
> Sandia National Laboratories
> E-mail: jzimmer at sandia.gov
> ------------------------------------------
>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.