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

[Stefano de Gironcoli]

Ryd/au^2

stefano

On 11/04/25 11:58, Shubham Patel wrote:
> 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/
>
> = 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/
>
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