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Dear Oliviero, <br>
<br>
thanks for your email. I know the paper you mentioned, but I thought
(wrongly apparently) that this approach was only implemented in cp.x
(the &PRESS-AI namelist). Also I was not really sure this could
be used for applying a uniaxial stress on an isolated system. The
pressure is accounted for by considering the PV term in the
enthalpy, with a volume computed from rho. In the case of a uniaxial
compression, one should instead define a surface where the stress
should be present? I did not see how it could be done. This is why I
considered forces on ions instead of forces on electrons. <br>
It would be interesting to study whether these different approaches
could imply different mechanical behaviors ! <br>
<br>
Best regards<br>
<br>
Laurent <br>
<br>
<br>
<div class="moz-cite-prefix">On 27/05/2021 22:34, Andreussi,
Oliviero wrote:<br>
</div>
<blockquote type="cite"
cite="mid:D439A443-44A9-4D97-812D-A62310C0CC9A@unt.edu">
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Dear Laurent,
<div class=""><br class="">
</div>
<div class="">I am not fully sure about the details of your
implementation and I am not commenting on the best place to put
your keywords (as Paolo said, Environ adopts an external file
for its own input). I mostly wanted to mention that Environ
allows you to introduce an external pressure into the system.
With the right settings this could be used to apply a
compressive pressure on rigid planes above or below a slab or,
using a cylindrical symmetry, on a nanowire (but also to a
isolated system, as per Cococcioni et al,
PRL 10.1103/PhysRevLett.94.145501).</div>
<div class=""><br class="">
</div>
<div class="">Best,</div>
<div class=""><br class="">
</div>
<div class="">Oliviero</div>
<div class=""> <br class="">
<div class=""><br class="">
<div class="">
<div dir="auto" style="caret-color: rgb(0, 0, 0); color:
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class="">
<div dir="auto" style="caret-color: rgb(0, 0, 0); color:
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<div style="caret-color: rgb(0, 0, 0); color: rgb(0,
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none;">
Oliviero Andreussi<br class="">
--<br class="">
Assistant Professor<br class="">
Department of Physics<br class="">
University of North Texas<br class="">
<a href="mailto:oliviero.andreussi@unt.edu" class=""
moz-do-not-send="true">Email: oliviero.andreussi@unt.edu</a> </div>
<div style="caret-color: rgb(0, 0, 0); color: rgb(0,
0, 0); font-family: Helvetica; font-size: 12px;
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none;">
Phone: +1-(940)-369-5316<br class="">
Skype: olivieroandreussi<br class="">
Web: <a href="https://www.materialab.org" class=""
moz-do-not-send="true">https://www.materialab.org</a></div>
</div>
</div>
</div>
</div>
<div><br class="">
<blockquote type="cite" class="">
<div class="">On May 27, 2021, at 3:04 PM, Paolo Giannozzi
<<a href="mailto:paolo.giannozzi@uniud.it" class=""
moz-do-not-send="true">paolo.giannozzi@uniud.it</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">Dear Laurent<br class="">
<br class="">
the proliferation of input variables in QE is an old
and known problem. I am not sure what the best
solution should be, though. One possibility I would
consider is to read the needed variables from a
separate file.<br class="">
If I remember correctly this is what the "Environ"
library does.<br class="">
Another one is to extend the existing ATOMIC_FORCES
card, that currently supports only a list of forces,
to cover your case as well.<br class="">
<br class="">
Paolo<br class="">
<br class="">
On 27/05/2021 10:00, Laurent Pizzagalli wrote:<br
class="">
<blockquote type="cite" class="">Dear Dr. Giannozzi,<br
class="">
I write to you concerning the implementation of an
external force field in quantum espresso. The
motivation is the investigation of the mechanical
properties of nanoparticles, especially in the
plastic regime, obtained by uniaxial compression.
The implementation is not complicated, since you
(the developers) had already planned this
potentiality in the file 'plugin_ext_forces.f90'.<br
class="">
Actually, i already made the implementation in cp.x,
but in a quick way, in a local copy of the code.
Since it is successful, I would like to do it
properly, merging it with the development version
using git. I got almost all the information I need
in the developer manual. But I still have one
question, concerning the general organization of the
input. Right now, I implemented only one kind of
force field, fully repulsive. It allows for
compressing the nanoparticle between two planes. Six
keywords are needed, one for the activation of the
force field, four to define the position of the
planes and the increment for their displacements at
each timestep, and a last one to define the strength
of the repulsion. My question is: what would be the
best way to organize these keywords? Originally, I
put all of these into the &IONS namelist.
Another option would be in the &SYSTEM namelist.
And finally, maybe it would be better to create a
specific NAMELIST to include these keywords
(something like &EXTFF)? I also plan to
implement another force field (including an
attractive interaction), which would require other
keywords. So the creation of a specific NAMELIST
seems the best option in my opinion. But I would
like to have yours before proceeding.<br class="">
Best regards<br class="">
Laurent<br class="">
</blockquote>
<br class="">
-- <br class="">
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche
e Fisiche,<br class="">
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br
class="">
Phone +39-0432-558216, fax +39-0432-558222<br class="">
_______________________________________________<br
class="">
developers mailing list<br class="">
<a href="mailto:developers@lists.quantum-espresso.org"
class="" moz-do-not-send="true">developers@lists.quantum-espresso.org</a><br
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</div>
</div>
</blockquote>
</div>
<br class="">
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
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--------------------------------------------------oOOO--(_)--OO|o------
<a class="moz-txt-link-rfc2396E" href="mailto:Laurent.Pizzagalli@univ-poitiers.fr"><Laurent.Pizzagalli@univ-poitiers.fr></a>
<a class="moz-txt-link-freetext" href="http://laurent.pizzagalli.free.fr/">http://laurent.pizzagalli.free.fr/</a> Tel +33 549 49 74 99
------------------------------------------ Fax +33 549 49 66 92
Institut P'
Departement de Physique et de Mécanique des Matériaux
CNRS UPR 3346
Université de Poitiers
SP2MI
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----------------------------------------------------\ (----( )-------
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