[QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues

[Shubham Patel]

Dear Prof. Stefano, 

Thank you for your reply. I did not receive your message on my email that is why I missed it. 

When I diagonalize the q dependent matrices I can obtain the eigenvalues (frequencies) from which I am getting the correct phonon dispersion but the frequency range is not correct as I had shown in a figure I previously attached. Even if I multiply now with 13.6 eV (13600 meV) to convert Ryd to meV I am not able to reproduce the frequency range. Could you please suggest what factor I am missing here? 

Thank you very much. 

Sincerely, 
Shubham 


From: "Stefano de Gironcoli" <degironc at sissa.it> 
To: "Quantum ESPRESSO users Forum" <users at lists.quantum-espresso.org> 
Sent: Tuesday, April 15, 2025 9:25:04 PM 
Subject: Re: [QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues 

Ryd/au^2 ... as already stated in my previous reply 
Stefano 

Get [ https://aka.ms/AAb9ysg | 
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From: users <users-bounces at lists.quantum-espresso.org> on behalf of Shubham Patel <spatelphy at iitkgp.ac.in> 
Sent: Tuesday, April 15, 2025 5:45:37 PM 
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org> 
Subject: Re: [QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues 
Hello again, 

Could anyone please tell? 

Sincerely, 
Shubham 

----- Original Message ----- 
From: "Shubham Patel" <spatelphy at iitkgp.ac.in> 
To: "Quantum ESPRESSO users Forum" <users at lists.quantum-espresso.org> 
Sent: Friday, April 11, 2025 3:28:53 PM 
Subject: Re: [QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues 

Hi, 

Could someone please tell what is the unit of dynamical matrix elements'. I have to do some post processing from the dynamical matrices and therefore I want to know the proper units of the elements. 

Thank you, 
Shubham 

----- Original Message ----- 
From: "Shubham Patel" <spatelphy at iitkgp.ac.in> 
To: "Quantum ESPRESSO users Forum" <users at lists.quantum-espresso.org> 
Sent: Wednesday, April 9, 2025 8:09:58 AM 
Subject: Re: [QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues 

Dear Kazume NISHIDATE, 

Thank you very much for your prompt reply. This is indeed correct what you observed. However, when I divide the y scale of right hand side figure with 0.005 it should return the left figure but it does not. Attaching the modified figure in the right most (dividing with 0.005). Am I missing something? 

Thank you, 
Shubham 

----- Original Message ----- 
From: "Kazume NISHIDATE" <nisidate at iwate-u.ac.jp> 
To: "Quantum ESPRESSO users Forum" <users at lists.quantum-espresso.org> 
Sent: Wednesday, April 9, 2025 1:54:59 AM 
Subject: Re: [QE-users] unit mismatch between PH generated frequencies and manually generated eigenvalues 

Dear Shubham, 

I’m not an expert on the phonon calculation. 
But it may be in a wavelength unit. 

The bottom of the curve in the left-hand graph is around 25 meV. 

25 meV = 0.025 eV 

0.025 eV is around 50 micro m (wavelength). 
[ https://sherwingroup.itst.ucsb.edu/internal/unit-conversion/ | https://sherwingroup.itst.ucsb.edu/internal/unit-conversion/ ] 

= 50 x 10^(-6) m 
= 50 x 10^(-6) x 100 cm 
= 50 x 10^(-4) cm 
= 5 x 10^(-3) cm 
= 0.005 cm 

It is around the bottom of the curve in the right-hand graph. 



> 2025/04/09 0:03、Shubham Patel <spatelphy at iitkgp.ac.in>のメール: 
> 
> Dear developers and users, 
> 
> I am trying to calculate the frequencies (freqs) using Quantum Espresso PHonon calculations as well as using dynamical matrices generated using matdyn.x. I find that there is a unit mismatch in the freqs which gives rise to a magnitude difference. In the first case, I calculate phonon band structure using matdyn.x --> plotband.x. While in the second case I generate dynamical matrices using matdyn.x and then diagonalize the matrices along the kpath and generated exactly same band dispersion except the magnitude on the y-axis (frequency range). Could anyone please tell what is this factor which brings the magnitude mismatch? I am also attaching a figure to compare. 
> 
> Thank you very much for any help. 
> 
> Sincerely, 
> Shubham<phdos_AZX_mimatch.pdf>__________________________________________________ 



西館数芽 
Kazume NISHIDATE Ph.D 

Department of Systems Innovation Engineering, 
Graduate School of Science and Engineering, Iwate University 
4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN 
Phone:+81-19-621-6391 
kazume.nishidate at gmail.com, nisidate at iwate-u.ac.jp 
[ https://sites.google.com/site/nisidatelab/ | https://sites.google.com/site/nisidatelab/ ] 

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-------------------------------------------------------------------------------- 
Quantum ESPRESSO is supported by MaX ( [ http://www.max-centre.eu/ | www.max-centre.eu ] ) 
users mailing list users at lists.quantum-espresso.org 
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_______________________________________________________________________________ 
The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare. 
-------------------------------------------------------------------------------- 
Quantum ESPRESSO is supported by MaX (www.max-centre.eu) 
users mailing list users at lists.quantum-espresso.org 
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