[QE-users] asr in dynmat.x

Thu Jun 8 11:37:06 CEST 2023

Thanks, Paolo and Lorenzo, for your comments.
I will do some tests for the threshold.
But let me point out that this is bulk MoS2, not 2D.

Regards,

Juliana
-----
Dr Juliana Morbec
Lecturer in Physics
Keele University, UK
________________________________
From: Lorenzo Bastonero <lbastone at uni-bremen.de>
Sent: Thursday, June 8, 2023 10:22:39 AM
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Cc: Juliana Maria Abreu Da Silva Morbec <j.morbec at keele.ac.uk>
Subject: Re: [QE-users] asr in dynmat.x

Dear Juliana,

Indeed the ASR in the old QE version did not include the correct rotational invariants for 2D systems, i.e. you should have 4 acoustic modes at Gamma that are zero.

Although, having a closer look to your inputs, I would suggest you to pay attention to:
1. Why have you commented out ‘assume_isolated’? That is usually important to get rid of the long-range planar interaction between images.
2. The threshold for phonons seem a bit too low. Did you do some tests? In my experience that threshold should be much lower, e.g. 1e-16/18.

HTH,
Lorenzo

********************************
Lorenzo Bastonero

PhD Student
U Bremen Excellence Chair,
Bremen Center for Computational Materials Science,
and MAPEX Center for Materials and Processes

University of Bremen
Faculty of Production Engineering
TAB-Building, Room 3.32
Am Fallturm 1
28359 Bremen, DE

http://www.hmi.uni-bremen.de/

Il giorno 8 giu 2023, alle ore 11:08, Paolo Giannozzi <paolo.giannozzi at uniud.it<mailto:paolo.giannozzi at uniud.it>> ha scritto:

I have heard that in 2D systems some acoustic sum rules may yield funny results for acoustic modes close to q=0. The latest 7.2 version of the code should contain an improved ASR. See https://gitlab.com/QEF/q-e/-/merge_requests/1978

Paolo

On 6/8/23 00:12, Juliana Maria Abreu Da Silva Morbec wrote:

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Dear Lorenzo.
Thanks for your response.
I am attaching here the input files for scf and phonon calculations of bulk MoS2, as well as output files of dynmat.x using asr='simple' and asr='crystal'. I also noticed that asr='no' give similar results to asr='crystal'.
Regards,
Juliana
-----
*Dr Juliana Morbec*
Lecturer in Physics
Keele University, UK
------------------------------------------------------------------------
*From:* users <users-bounces at lists.quantum-espresso.org<mailto:users-bounces at lists.quantum-espresso.org>> on behalf of Lorenzo Bastonero <lbastone at uni-bremen.de<mailto:lbastone at uni-bremen.de>>
*Sent:* 06 June 2023 14:28
*To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>>
*Subject:* Re: [QE-users] asr in dynmat.x
Dear Juliana,
In principle at Gamma the acoustic sum rules should only affect the 3 acoustic modes, setting them to 0, and leave the other modes close to their values ( ~< 1/0.1 cm-1).
If you are experiencing huge change in the wavenumber, it may probably be a sign of under converged calculations. Hard to say though w/o inputs/outputs.
HTH,
Lorenzo
********************************
Lorenzo Bastonero
PhD Student
U Bremen Excellence Chair,
Bremen Center for Computational Materials Science,
and MAPEX Center for Materials and Processes
University of Bremen
Faculty of Production Engineering
TAB-Building, Room 3.32
Am Fallturm 1
28359 Bremen, DE
http://www.hmi.uni-bremen.de/ <https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.hmi.uni-bremen.de%2F&data=05%7C01%7Cpaolo.giannozzi%40uniud.it%7C5e34b0384c774338a46708db67a47dc1%7C6e6ade15296c4224ac581c8ec2fd53a8%7C0%7C0%7C638217728437942031%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=MZqrRwY0Bzamr%2Fsf%2BViS9AHXAao%2FIhu%2BlACgy46NgV8%3D&reserved=0>
Il giorno 6 giu 2023, alle ore 15:14, Juliana Maria Abreu Da Silva Morbec <j.morbec at keele.ac.uk<mailto:j.morbec at keele.ac.uk> <mailto:j.morbec at keele.ac.uk>> ha scritto:

Hello.

I have a question regarding the 'asr' feature in dynmat.x. I am computing Raman spectra of MoS2 bulk and I noticed that asr='simple' and asr='crystal' give different frequencies but similar amplitude for Raman. And asr='crystal' seems to be in better agreement with experiments. How to decide which one to use?

Thank you,

Juliana Morbec
Lecturer in Physics
Keele University, UK
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