[QE-users] Parallelization and Input/Output of wfc in QE

[Pietro Davide Delugas]

Hello

To obtain the projected density of states for a particular atomic orbital you calculate  a weighted density of states , using as weight the square modulus  of the
projection of the wave-function to the atomic orbital.  In quantum-espresso this is done with the program projwfc.x

So  normal DOS is

[cid:image001.png at 01D9055B.40F9B610]

The projected density of states is

[cid:image002.png at 01D9055C.483BD0B0]

Hope this helps
Best regards, Pietro

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From: KRISHNENDU MUKHERJEE<mailto:krishnendu at nmlindia.org>
Sent: Wednesday, November 30, 2022 11:23 AM
To: users<mailto:users at lists.quantum-espresso.org>
Subject: [QE-users] Parallelization and Input/Output of wfc in QE


Dear Dr. Pietro,

 Thank you for your reply. I did not have a course on Quantum Mechanics and Solid State Physics. But I am currently reading thoroughly text books on those subjects. I have another question.
In Quantum Espresso the electron is considered to be described by plane-waves. So, it does not have information regarding its belongness to any particular s,p or d orbital. However, I have seen articles with Quantum Espresso results with DOS for a particular orbital (e.g., 3d). Can you kindly let me know how DOS of a particular orbital can be obtained from the plane-wave representation of electron?

Thank you,
Best regards,
Krishnendu

-------------------------------------------------------------------------------------------------------------------------------------------------------

Dear Krishnendu,

if you want to know what the grids are (those appearing in the header of
the table) check this message from Stefano de Gironcoli:

https://lists.quantum-espresso.org/pipermail/developers/2017-November/001783.html

The second keyword in that table is "sticks", which concerns with the
way the data is distributed among multiple processes in order to perform
a parallel FFT. This presentation, again by Prof. de Gironcoli, will
explain how that works:

https://www.youtube.com/watch?v=YqYdu1aVi-o

With these information and the details of your input file (ecutwfc,
ecutrho and the lattice) you should be able to roughly predict the
number of G-vectors of the various grids of your plane wave expansion.
Predicting the number of sticks is slightly more complicated and, in my
opinion, it's quite pointless.

Best wishes,
Pietro

---

Pietro Bonfà
Università di Parma


On 11/29/22 12:56, KRISHNENDU MUKHERJEE wrote:
>
> How many G-vectors are required to describe a plane-wave ?
>
> It will be very helpful if I could understand the following part of the
> output that I am getting almost in the beginning.
>
> G-vector sticks info
>       --------------------
>       sticks:   dense  smooth     PW     G-vecs:    dense   smooth      PW
>       Sum        6181    3093    885               364637   128843   20341
>
> Thank you,
> Regards,
>
> Krishnendu
>
> ------------------------------------------------------------------------------------------------------------------------------------------
>
> Actually, all the coefficients of all the wavefunctions AT A GIVEN K
> POINT: there is one wavefunction file per k point.
>
> Paolo
>
> On 11/28/22 14:07, Riccardo Piombo uniroma1 via users wrote:
>>/So in a single file QE stores ALL the coefficients of ALL the wfcs? />//>/Is it correct? />//>//>/Thanks for your help, />//>/Riccardo Piombo />//




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