[QE-users] How does one calculate dipole moments or access (readable) wave functions from e.g. PW?

Wed Aug 9 11:41:33 CEST 2023

Thank you Stefano! I was actually searching for a better reference but 
did not think about your Rev. Mod. Phys. which I usually suggest to our 
students for reading and understanding a bit more about DFPT. Concerning 
optical properties also this might be interesting: 
https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.74.601

On 8/9/23 11:30, Stefano Baroni wrote:
>
> Hi All. Many thanks for this interesting discussion.
>
> Thomas: the literature you recommend 
> (https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F) 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 
> https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.73.515
>
> Best regards – SB
>
> *From: *users <users-bounces at lists.quantum-espresso.org> on behalf of 
> Thomas Brumme <tbrumme at msx.tu-dresden.de>
> *Date: *Wednesday, 9 August 2023 at 11:13
> *To: *Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>, 
> Brian de Keijzer <briandekeyzer at hotmail.com>
> *Subject: *Re: [QE-users] How does one calculate dipole moments or 
> access (readable) wave functions from e.g. PW?
>
> Dear Brian,
>
> Sorry to be a bit blunt but your question cannot be answered in a
> one-liner and indicates that
> you might miss a few important points.
>
> I guess you have read the input description of bands.x and since you're
> are still asking how to
> get the dipole matrix elements you are probably unaware of the fact that
> those are not well
> defined in solids. Well, at least the position operator is not well
> defined in an infinite solid
> because every point could be the origin. Thus, one has to use the
> momentum operator instead.
> (see, e.g., Eq. (7) in this paper
> https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.80.1800)
>
> I suggest to read some publications first, books, in order to understand
> what you need to do.
> This paper seems quite useful - I didn't read it carefully though but
> just found it via a quick
> Google search:
>
> https://pubs.rsc.org/en/content/articlelanding/2023/CP/D2CP05991F
>
> If you're interested in optical properties then there are many more
> things to take into account.
> A good starting point might be the pages of the Yambo code, in
> particular this:
>
> https://www.yambo-code.eu/wiki/index.php/Main_Page
>
> and more specifically the thesis of Andrea Marini has a good collection
> of the equations and
> references
>
> https://www.yambo-code.eu/wiki/images/2/20/Marini_PhD.pdf
>
> In a nutshell: you need to calculate the dielectric function and then
> there are different
> approximations involved.
>
> Kind regards
>
> Thomas
>
> On 8/9/23 09:27, Brian de Keijzer wrote:
> > Hi all,
> >
> >
> > Would anyone know how one retrieves the dipole matrix elements from 
> bands.x (or in another way?)?
> >
> > Any help is appreciated.
> >
> >
> > Bests,
> >
> > Brian de Keijzer
> >
> >> On 25 Jul 2023, at 16:09, Brian de Keijzer 
> <briandekeyzer at hotmail.com> wrote:
> >>
> >> Hi Paolo,
> >>
> >> Thank you for your answer’
> >>
> >> 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?
> >>
> >> 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.
> >>
> >> Best regards,
> >>
> >> Brian de Keijzer
> >>
> >>> On 25 Jul 2023, at 13:37, Paolo Giannozzi 
> <paolo.giannozzi at uniud.it> wrote:
> >>>
> >>> I think code "bands.x" can compute dipole matrix elements.
> >>>
> >>> 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.
> >>>
> >>> Paolo
> >>>
> >>>> On 7/25/23 10:40, Brian de Keijzer wrote:
> >>>> [You don't often get email from briandekeyzer at hotmail.com. Learn 
> why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >>>> Hi all,
> >>>> 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?
> >>>> 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.
> >>>> 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.
> >>>> Bests,
> >>>> Brian de Keijzer
> >>>> _______________________________________________
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> >>> --
> >>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> >>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> >>> Phone +39-0432-558216, fax +39-0432-558222
> > _______________________________________________
> > The Quantum ESPRESSO community stands by the Ukrainian
> > people and expresses its concerns about the devastating
> > effects that the Russian military offensive has on their
> > country and on the free and peaceful scientific, cultural,
> > and economic cooperation amongst peoples
> > _______________________________________________
> > Quantum ESPRESSO is supported by MaX (www.max-centre.eu 
> <http://www.max-centre.eu>)
> > users mailing list users at lists.quantum-espresso.org
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>
> -- 
> Dr. rer. nat. Thomas Brumme
> Theoretical chemistry
> TU Dresden - KOE / 103
> Bergstr. 66c
> 01069 Dresden
>
> Tel:  +49 (0)351 463 39449
>
> email: thomas.brumme at tu-dresden.de
>
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu 
> <http://www.max-centre.eu>)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing listusers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users

-- 
Dr. rer. nat. Thomas Brumme
Theoretical chemistry
TU Dresden - KOE / 103
Bergstr. 66c
01069 Dresden

Tel:  +49 (0)351 463 39449

email:thomas.brumme at tu-dresden.de
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