Hello,
there is a bug in QE version 7.2 for exchange_only functionals in libxc, that 
has been fixed in the develop version.
If you do not want to download the develop branch, tou just have to add the two 
following lines:

  *   xcoef=1.d0
  *   if (ishybrid .and. exx_started .and. exx_fraction>0.d0) 
xcoef=1.d0-exx_fraction

at line 355 of XClib/xc_wrapper_gga.f90 and then recompile.
Cheers,
Fabrizio

CNR IOM

________________________________
From: users <users-boun...@lists.quantum-espresso.org> on behalf of Ayoub 
Aouina <ayoubaou...@outlook.com>
Sent: Thursday, August 10, 2023 9:28 PM
To: users@lists.quantum-espresso.org <users@lists.quantum-espresso.org>
Subject: [QE-users] difference between the internal PBE and the libxc one


Dear all,

I'm currently facing an issue with the use of Libxc for PBE calculations in 
Quantum ESPRESSO. I'm noticing a significant discrepancy in results when 
comparing the internal PBE functional (input_dft = "PBE") to using Libxc with 
the PBE functional (input_dft = "XC-000I-000I-101L-130L-000I-000I").

  *   For internal PBE: Total energy contribution from xc is -4.83542517 Ry.
  *   For Libxc PBE (input_dft = "XC-000I-000I-101L-130L-000I-000I"): Total 
energy contribution from xc is -0.63113373 Ry.

I'm reaching out to seek insights into why such a substantial difference might 
occur between these calculations. I wonder if there are specific external 
parameters that need to be set when utilizing the PBE functional from Libxc.

I would also like to ask why the xc contributions are not printed in the output 
file for some hybrid functionals like : B3LYP?

Attached is my input file and the pseudo-potential file for a Silicon 
calculation. Any guidance or recommendations would be highly appreciated.

Best regards,

--
Ayoub Aouina, PhD.,
Institut für Festkörpertheorie und -optik
Friedrich-Schiller-Universität Jena
Max-Wien-Platz 1
07743 Jena
Germany

Mail: ayoub.aou...@uni-jena.de<mailto:ayoub.aou...@uni-jena.de>
_______________________________________________
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
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users

Reply via email to