[QE-developers] Raman spectra with LDA(GGA)+U

Sun Jul 3 11:33:51 CEST 2022

While the documentation of ph.x seems to state that, among other things, ph.x does not work with LDA+U, looking at the github past issues, I am under the impression that it might. Can anyone verify this. I have a small anti-fermomagnetic system that is metallic without GGA+U with Vasp and Castep, but insulating with LDA+U using self-consistently derived values for U (using Vasp). CASTEP unfortunately doesn’t handle magnetic systems yet for Raman. While Vasp can carry out Raman calculations using phon3py, the calculations are very onerous due to the need to numerically calculate higher order derivatives. If it is possible to use DFPT with LDA(GGA)+U in QE 7.0 or QE 7.1?

Thanks.

Paul Fons
paulfons at keio.jp

Keio University, Faculty of Science and Technology, Department of Electronics and Electrical Engineering

〒223-8522 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
Keio University Faculty of Science and Technology Yagami Campus.

〒223-8522　横浜市港北区日吉3-14-1 慶應義塾大学理工学部電気情報工学科 23-315　

> On Jun 27, 2022, at 16:20, Paolo Giannozzi <paolo.giannozzi at uniud.it> wrote:
> 
> On 26/06/2022 18:17, Soumendra Kumar Das wrote:
> 
>> I am using quantum espresso for superconductivity Tc calculation. I put this question last week in the QE users forum but I did not get any response.
> 
> your message was held because too large
> 
>> I was trying to calculate the superconducting transition temperature of Pb and Al given as trial example in the phonon calculation of QE. all the steps are running successfully. only the last step is giving "NaN" (not a number).
>> I am requesting to kindly suggest to me what I should do and why this error is coming.
> 
> the utility 'lambda.x' is basically unmaintained, because there are much better ways to compute electron-phonon quantities (e.g. using EPW). I plan to have a look at the entire electron-phonon stuff sooner or later but it is not high in my list of priorities. In the meantime: most likely, the NaN comes from a acoustic phonons with "negative" frequencies at q=0. These contribute nothing to the lambda, so you may just try to set them explicitly to zero, or to a small positive value. The lambda.x code is very simple and one can just look inside it to see what happens and why
> 
> Paolo
> 
>> I am sending  both the input and output data for lambda.x calculation. The tutorial file which I was following is also attached here.
>> ###########################################################################
>> 10 0.12 1 ! emax (something more than highest phonon mode in THz), degauss, smearing method
>> 8 ! Number of q-points for which EPC is calculated,
>> 0.0000000 0.0000000 0.0000000 1.00 ! the first q-point, use kpoints.x program to calculate
>> -0.2500000 -0.2500000 0.2500000 8.00 ! q-points and their weight
>> -0.5000000 -0.5000000 0.5000000 4.00 !
>> 0.0000000 0.0000000 0.5000000 6.00 ! 4th q-point, qx,qy,qz
>> -0.2500000 -0.2500000 0.7500000 24.00 !
>> -0.5000000 -0.5000000 1.0000000 12.00 !
>> 0.0000000 0.0000000 1.0000000 3.00 !
>> -0.5000000 0.0000000 1.0000000 6.00 ! the last q-point
>> elph_dir/elph.inp_lambda.1 ! elph output file names,
>> elph_dir/elph.inp_lambda.2 ! in the same order as the q-points before
>> elph_dir/elph.inp_lambda.3
>> elph_dir/elph.inp_lambda.4
>> elph_dir/elph.inp_lambda.5
>> elph_dir/elph.inp_lambda.6
>> elph_dir/elph.inp_lambda.7
>> elph_dir/elph.inp_lambda.8
>> 0.10 ! \mu the Coloumb coefficient in the modified
>> ! Allen-Dynes formula for T_c (via \omega_log)
>> ######################################################################
>> lambda = 0.242639 ( NaN ) <log w>= NaN K N(Ef)= 1.294938 at degauss= 0.005
>> lambda = 0.350909 ( NaN ) <log w>= NaN K N(Ef)= 1.845335 at degauss= 0.010
>> lambda = 0.348256 ( NaN ) <log w>= NaN K N(Ef)= 2.071123 at degauss= 0.015
>> lambda = 0.324666 ( NaN ) <log w>= NaN K N(Ef)= 2.196774 at degauss= 0.020
>> lambda = 0.302942 ( NaN ) <log w>= NaN K N(Ef)= 2.275654 at degauss= 0.025
>> lambda = 0.289683 ( NaN ) <log w>= NaN K N(Ef)= 2.340134 at degauss= 0.030
>> lambda = 0.283603 ( NaN ) <log w>= NaN K N(Ef)= 2.397743 at degauss= 0.035
>> lambda = 0.281253 ( NaN ) <log w>= NaN K N(Ef)= 2.449225 at degauss= 0.040
>> lambda = 0.280253 ( NaN ) <log w>= NaN K N(Ef)= 2.493764 at degauss= 0.045
>> lambda = 0.279197 ( NaN ) <log w>= NaN K N(Ef)= 2.530433 at degauss= 0.050
>> lambda omega_log T_c
>> 0.24264 NaN NaN
>> 0.35091 NaN NaN
>> 0.34826 NaN NaN
>> 0.32467 NaN NaN
>> 0.30294 NaN NaN
>> 0.28968 NaN NaN
>> 0.28360 NaN NaN
>> 0.28125 NaN NaN
>> 0.28025 NaN NaN
>> 0.27920 NaN NaN
>> -- 
>> *---------------------------------------*
>> *Thanks and Regards*
>> *Soumendra Kumar Das*
>> *Postdoc. Research Scholar*
>> *School of Physical Sciences*
>> *National Institute of Science Education and Research (NISER), **Bhubaneswar*
>> *PO- Bhimpur-Padanpur, Via- Jatni, District:- Khurda*
>> *PIN – 752050, Odisha, INDIA*
>> ________________________________________________
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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.
> _______________________________________________
> developers mailing list
> developers at lists.quantum-espresso.org <mailto:developers at lists.quantum-espresso.org>
> https://lists.quantum-espresso.org/mailman/listinfo/developers <https://lists.quantum-espresso.org/mailman/listinfo/developers>
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