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<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US">Hi All. Many thanks for this interesting discussion.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US">Thomas: the literature you recommend (</span><span style="font-size:11.0pt"><a href="https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F">https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F</a></span><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US">)
is rather ill informed. It overlooks the fact that the problem of a proper definition of the position operator in the calculation of dielectric and optical properties is as old (actually older) than density-functional perturbation theory. None of the original
literature is properly cited. A better informed reference, with a historically accurate account of the relevant literature is
<a href="https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.73.515">https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.73.515</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US">Best regards – SB<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:Helvetica;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">users <users-bounces@lists.quantum-espresso.org> on behalf of Thomas Brumme <tbrumme@msx.tu-dresden.de><br>
<b>Date: </b>Wednesday, 9 August 2023 at 11:13<br>
<b>To: </b>Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org>, Brian de Keijzer <briandekeyzer@hotmail.com><br>
<b>Subject: </b>Re: [QE-users] How does one calculate dipole moments or access (readable) wave functions from e.g. PW?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Dear Brian,<br>
<br>
Sorry to be a bit blunt but your question cannot be answered in a <br>
one-liner and indicates that<br>
you might miss a few important points.<br>
<br>
I guess you have read the input description of bands.x and since you're <br>
are still asking how to<br>
get the dipole matrix elements you are probably unaware of the fact that <br>
those are not well<br>
defined in solids. Well, at least the position operator is not well <br>
defined in an infinite solid<br>
because every point could be the origin. Thus, one has to use the <br>
momentum operator instead.<br>
(see, e.g., Eq. (7) in this paper <br>
<a href="https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.80.1800)">https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.80.1800)</a><br>
<br>
I suggest to read some publications first, books, in order to understand <br>
what you need to do.<br>
This paper seems quite useful - I didn't read it carefully though but <br>
just found it via a quick<br>
Google search:<br>
<br>
<a href="https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F">https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F</a><br>
<br>
If you're interested in optical properties then there are many more <br>
things to take into account.<br>
A good starting point might be the pages of the Yambo code, in <br>
particular this:<br>
<br>
<a href="https://www.yambo-code.eu/wiki/index.php/Main_Page">https://www.yambo-code.eu/wiki/index.php/Main_Page</a><br>
<br>
and more specifically the thesis of Andrea Marini has a good collection <br>
of the equations and<br>
references<br>
<br>
<a href="https://www.yambo-code.eu/wiki/images/2/20/Marini_PhD.pdf">https://www.yambo-code.eu/wiki/images/2/20/Marini_PhD.pdf</a><br>
<br>
In a nutshell: you need to calculate the dielectric function and then <br>
there are different<br>
approximations involved.<br>
<br>
Kind regards<br>
<br>
Thomas<br>
<br>
On 8/9/23 09:27, Brian de Keijzer wrote:<br>
> Hi all,<br>
><br>
><br>
> Would anyone know how one retrieves the dipole matrix elements from bands.x (or in another way?)?<br>
><br>
> Any help is appreciated.<br>
><br>
><br>
> Bests,<br>
><br>
> Brian de Keijzer<br>
><br>
>> On 25 Jul 2023, at 16:09, Brian de Keijzer <briandekeyzer@hotmail.com> wrote:<br>
>><br>
>> Hi Paolo,<br>
>><br>
>> Thank you for your answer’<br>
>><br>
>> Bands.x had caught my eye before but I did not notice how to make it output transition dipole moments. How would one compute those?<br>
>><br>
>> Meanwhile I managed to indeed get hdf5 output. That’s great! If there is a native way to obtain the values I want it’s preferable tho.<br>
>><br>
>> Best regards,<br>
>><br>
>> Brian de Keijzer<br>
>><br>
>>> On 25 Jul 2023, at 13:37, Paolo Giannozzi <paolo.giannozzi@uniud.it> wrote:<br>
>>><br>
>>> I think code "bands.x" can compute dipole matrix elements.<br>
>>><br>
>>> About direct access to wavefunctions: the default fortran binary format is basically unreadable except via the routines of QE. One may optionally write hdf5 files that are much easier to read with external utilities, though.<br>
>>><br>
>>> Paolo<br>
>>><br>
>>>> On 7/25/23 10:40, Brian de Keijzer wrote:<br>
>>>> [You don't often get email from briandekeyzer@hotmail.com. Learn why this is important at
<a href="https://aka.ms/LearnAboutSenderIdentification">https://aka.ms/LearnAboutSenderIdentification</a> ]<br>
>>>> Hi all,<br>
>>>> New QE users here. I’ve used QE so far to compute band structures for crystals. I am however very much interested in calculating the dipole matrix elements for said crystals. Does QE have a module that allows one to do this? If so, how would that work?<br>
>>>> Moreover, I have read that it is possible to use the wave functions directly. That would allow me to compute the dipole elements. Unfortunately most posts that I come across appear to be a bit dated tho. What would be the best way to access the wave functions
using more recent versions of e.g. Python? I’ve come across postqe but that appears to no longer be in development nor does the installation work on my Python 3.9 distribution.<br>
>>>> Anyhow; I’m looking to learn how to compute k-dependent transition dipole moments in QE. It would be awesome if anyone would want to provide an outline of how such a thing is to be done using the latest version of QE.<br>
>>>> Bests,<br>
>>>> Brian de Keijzer<br>
>>>> _______________________________________________<br>
>>>> The Quantum ESPRESSO community stands by the Ukrainian<br>
>>>> people and expresses its concerns about the devastating<br>
>>>> effects that the Russian military offensive has on their<br>
>>>> country and on the free and peaceful scientific, cultural,<br>
>>>> and economic cooperation amongst peoples<br>
>>>> _______________________________________________<br>
>>>> Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu">www.max-centre.eu</a>)<br>
>>>> users mailing list users@lists.quantum-espresso.org<br>
>>>> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
>>> -- <br>
>>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
>>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
>>> Phone +39-0432-558216, fax +39-0432-558222<br>
> _______________________________________________<br>
> The Quantum ESPRESSO community stands by the Ukrainian<br>
> people and expresses its concerns about the devastating<br>
> effects that the Russian military offensive has on their<br>
> country and on the free and peaceful scientific, cultural,<br>
> and economic cooperation amongst peoples<br>
> _______________________________________________<br>
> Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu">www.max-centre.eu</a>)<br>
> users mailing list users@lists.quantum-espresso.org<br>
> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
<br>
-- <br>
Dr. rer. nat. Thomas Brumme<br>
Theoretical chemistry<br>
TU Dresden - KOE / 103<br>
Bergstr. 66c<br>
01069 Dresden<br>
<br>
Tel: +49 (0)351 463 39449<br>
<br>
email: thomas.brumme@tu-dresden.de<br>
<br>
_______________________________________________<br>
The Quantum ESPRESSO community stands by the Ukrainian<br>
people and expresses its concerns about the devastating<br>
effects that the Russian military offensive has on their<br>
country and on the free and peaceful scientific, cultural,<br>
and economic cooperation amongst peoples<br>
_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu">www.max-centre.eu</a>)<br>
users mailing list users@lists.quantum-espresso.org<br>
<a href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a><o:p></o:p></span></p>
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