<!DOCTYPE html>
<html data-lt-installed="true">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body style="padding-bottom: 1px;">
<p><br>
</p>
<div class="moz-cite-prefix">On 29/08/2024 14:25, Alex Kirkpatrick
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:PAXP192MB1278A36C3EB13519D3391BC99B962@PAXP192MB1278.EURP192.PROD.OUTLOOK.COM">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<style type="text/css" style="display:none;">P {margin-top:0;margin-bottom:0;}</style>
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
You've given me an interesting direction to follow, thanks for
the info!</div>
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Just for curiosity's sake, is the problem with the idea of
'adding a free electron pseudo' because it means a very
different thing in QE code than 'adding a particle to the
simulation that acts like an electron'?</div>
</blockquote>
<p><br>
</p>
<p>A pseudopotential is a modelisation of the atom nuclei + the core
electrons which are assumed to be rigid, and their effect on the
valence atoms. It is inherently a rigid object. You choose where
to put the pseudopotentials in the unit cell, then the code adds
the necessary amount of electrons to neutralize them, these
electrons are free to delocalize and float around in order to
minimize the total energy.<br>
</p>
<p>It is not totally completely absurd to conceive a pseudopotential
like a point-charge has a negative charge, i.e. a potential of
form -q/r, then assign to it the electron mass and compute the
force acting on it, but it would probably break a lot of implicit
assumptions that have been made in the code. </p>
<p>For example, I once tried to do a pseudopotential for a noble gas
with zero electrons in valence, and it totally did not work
properly, what you propose is even more extreme.</p>
<p><br>
</p>
<p>hth<br>
</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:PAXP192MB1278A36C3EB13519D3391BC99B962@PAXP192MB1278.EURP192.PROD.OUTLOOK.COM">
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Kind regards,</div>
<div class="elementToProof"
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="Signature">
<p>Sent from <a href="http://aka.ms/weboutlook"
id="OWAbf846a9e-c156-ad67-7b71-6238d1b1bbc1"
class="OWAAutoLink"
style="margin-top: 0px; margin-bottom: 0px;"
moz-do-not-send="true">
Outlook</a><br>
</p>
</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<hr style="display: inline-block; width: 98%;">
<div id="divRplyFwdMsg" dir="ltr"><span
style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> Lorenzo
Paulatto <a class="moz-txt-link-rfc2396E" href="mailto:lorenzo.paulatto@cnrs.fr"><lorenzo.paulatto@cnrs.fr></a><br>
<b>Sent:</b> 29 August 2024 11:27<br>
<b>To:</b> Alex Kirkpatrick
<a class="moz-txt-link-rfc2396E" href="mailto:canilivehere@hotmail.co.uk"><canilivehere@hotmail.co.uk></a>; Quantum ESPRESSO users
Forum <a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a><br>
<b>Subject:</b> Re: [QE-users] Pseudopotential to approximate
a free electron?</span>
<div> </div>
</div>
<div style="padding-bottom: 1px;">
<p style="margin-top: 0px; margin-bottom: 0px;"><br>
</p>
<div>On 29/08/2024 12:36, Alex Kirkpatrick wrote:</div>
<blockquote>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Thanks for the reply Lorenzo.</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I'm very new to all this but my thought was that, to have
some control over the distance between the 'electron' and
the surface, I would need to include it as a discrete
entity.</div>
</blockquote>
<p style="margin-top: 0px; margin-bottom: 0px;"><br>
</p>
<p style="margin-top: 0px; margin-bottom: 0px;">Hello, QE is a
code based on plane waves, which means that you cannot choose
where an electron goes. But I don't think you need to use an
explicit electron for your task. Thank to the power of
numerical simulation, you can plot/measure directly the
magnitude of the Kohn-Sham potential, (which is identical to
the Hartree electrostatic potential when you go in the
vacuum).</p>
<p style="margin-top: 0px; margin-bottom: 0px;">The procedure is
similar to the one explained in the workfunction example
(PP/examples/WorkFct_example) which shows how to compute the
average value of the electrostatic potential far away in the
vacuum to estimate the energy required to pull an electron
from the surface out to infinity.</p>
<p style="margin-top: 0px; margin-bottom: 0px;">Of course the
procedure is not entirely self-consistent (i.e. pulling out
the electron would change the potential) but for a metal it is
very close, and if you really need to you can remove some
amount of charge fro mthe surface using a positive value for
tot_charge</p>
<p style="margin-top: 0px; margin-bottom: 0px;">hth</p>
<p style="margin-top: 0px; margin-bottom: 0px;"><br>
</p>
<blockquote>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I would then be able to vary the distance and see how things
change. Is this the wrong way to go about it?</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Kind regards</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Alex</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="x_Signature">
<p style="margin-top: 0px; margin-bottom: 0px;">Sent from <a
href="http://aka.ms/weboutlook"
id="OWA410788d7-097b-d5e4-c088-7ef7ef96c719"
class="x_OWAAutoLink" data-auth="NotApplicable"
style="margin-top: 0px; margin-bottom: 0px;"
moz-do-not-send="true">
Outlook</a></p>
</div>
<div
style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<hr style="display: inline-block; width: 98%;">
<div id="x_divRplyFwdMsg" dir="ltr"><span
style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> users
<a href="mailto:users-bounces@lists.quantum-espresso.org"
id="OWA217b939f-74ac-32c7-a2b2-b0bd473b138d"
class="x_moz-txt-link-rfc2396E OWAAutoLink"
moz-do-not-send="true">
<users-bounces@lists.quantum-espresso.org></a> on
behalf of Lorenzo Paulatto <a
href="mailto:lorenzo.paulatto@cnrs.fr"
id="OWAfc2b0914-38ac-d6cb-63d9-a6ad17d7be8f"
class="x_moz-txt-link-rfc2396E OWAAutoLink"
moz-do-not-send="true">
<lorenzo.paulatto@cnrs.fr></a><br>
<b>Sent:</b> 29 August 2024 10:15<br>
<b>To:</b> Quantum ESPRESSO users Forum <a
href="mailto:users@lists.quantum-espresso.org"
id="OWA8b99705d-af82-7a96-f22d-cdd540baf361"
class="x_moz-txt-link-rfc2396E OWAAutoLink"
moz-do-not-send="true">
<users@lists.quantum-espresso.org></a><br>
<b>Subject:</b> Re: [QE-users] Pseudopotential to
approximate a free electron?</span>
<div> </div>
</div>
<div style="direction: ltr;">You could, probably, but why not
just use tot_charge=-1<br>
<br>
Kind regards</div>
<div style="direction: ltr;"><br>
<br>
</div>
<div style="direction: ltr;">On August 29, 2024 10:03:30 AM
GMT+02:00, Alex Kirkpatrick
<a href="mailto:canilivehere@hotmail.co.uk"
id="OWA2ba19da9-ba66-b9ab-6eef-95caccfbd84b"
class="x_moz-txt-link-rfc2396E OWAAutoLink"
moz-do-not-send="true">
<canilivehere@hotmail.co.uk></a> wrote:</div>
<blockquote
style="margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex; border-left: 1px solid rgb(204, 204, 204);">
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Dear all,</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Is it possible to create a pseudopotential file, or modify
an existing one like hydrogen, to approximate placing a
free electron in the simulation cell? </div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
The end goal being to model its interaction with material
surfaces in vacuum.</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Best wishes,</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Alex</div>
<div
style="direction: ltr; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="x_x_Signature">
<p style="margin-top: 0px; margin-bottom: 0px;">Sent from
<a href="http://aka.ms/weboutlook"
id="OWAa4a5971a-1f33-edf3-8da2-1463dfc94d2e"
class="x_OWAAutoLink" data-auth="NotApplicable"
style="margin-top: 0px; margin-bottom: 0px;"
moz-do-not-send="true">
Outlook</a></p>
</div>
</blockquote>
</blockquote>
<div>--<br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
id="OWA5644704d-5388-8f5a-d9a4-b629705fc357"
class="x_moz-txt-link-freetext OWAAutoLink moz-txt-link-freetext"
data-auth="NotApplicable" moz-do-not-send="true">http://www.impmc.upmc.fr/~paulatto/</a>
-
<a href="https://anharmonic.github.io/"
id="OWA7d7b3d34-9965-523f-a146-91ad2526bcd9"
class="x_moz-txt-link-freetext OWAAutoLink moz-txt-link-freetext"
data-auth="NotApplicable" moz-do-not-send="true">
https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05</small></div>
</div>
</blockquote>
<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
</body>
<lt-container></lt-container>
</html>