Re: [QE-users] question about last steps of vc-relax
Thanks Paolo! This is a chance to remind everyone that there are sets of carefully tested pseudopotentials (PBE and PBEsol) with suggested cutoffs on https://materialscloud.org/sssp ; these cover the entire periodic table. There are two choices - efficiency or precision. They have been verified again all electron calculations in https://arxiv.org/abs/2305.17274 - so consider these result scarefully - if your pseudopotential are not accueate, or cutoffs or samplings, your results will be incorrect. The QE input generator (not yet updated to the last SSSP 1.3) gives also some reasonable input parameters you can always use as a sanity check https://www.materialscloud.org/work/tools/qeinputgenerator nicola On 04/09/2023 11:42, Paolo Giannozzi wrote: On 9/4/23 11:09, Konstantin Glazyrin wrote: An example - target relaxation pressure 600 kbar: 1 - total stress (Ry/bohr**3) (kbar) P= 600.65 - last run of structure relaxation 2 - total stress (Ry/bohr**3) (kbar) P= 484.28 - final scf run May I ask - what does it indicate it indicates that your kinetic cutoff is too low for a good description of the pressure which value I should trust more and how should I proceed? the former is the pressure, computed for the plane-wave basis set of the INITIAL unit cell. The latter is the pressure, computed for the plane-wave basis set of the FINAL unit cell. They should converge to the same value at sufficiently high cutoff. Is it because of this? SCF correction compared to forces is large: reduce conv_thr to get better values For me it is conv_thr = 6.40d-06 it is a bit too large, but it is hardly related to the original problem Paolo Thank you! best wishes, Konstantin -- Beamline Scientist DESY, FS-PE, bldg. 47c, L115 Notkestrasse 85 22607 Hamburg, Germany ___ 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 -- -- Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL Director, National Centre for Competence in Research NCCR MARVEL, SNSF Head, Laboratory for Materials Simulations, Paul Scherrer Institut Contact info and websites at http://theossrv1.epfl.ch/Main/Contact ___ 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
Re: [QE-users] question about last steps of vc-relax
On 9/4/23 11:09, Konstantin Glazyrin wrote: An example - target relaxation pressure 600 kbar: 1 - total stress (Ry/bohr**3) (kbar) P= 600.65 - last run of structure relaxation 2 - total stress (Ry/bohr**3) (kbar) P= 484.28 - final scf run May I ask - what does it indicate it indicates that your kinetic cutoff is too low for a good description of the pressure which value I should trust more and how should I proceed? the former is the pressure, computed for the plane-wave basis set of the INITIAL unit cell. The latter is the pressure, computed for the plane-wave basis set of the FINAL unit cell. They should converge to the same value at sufficiently high cutoff. Is it because of this? SCF correction compared to forces is large: reduce conv_thr to get better values For me it is conv_thr = 6.40d-06 it is a bit too large, but it is hardly related to the original problem Paolo Thank you! best wishes, Konstantin -- Beamline Scientist DESY, FS-PE, bldg. 47c, L115 Notkestrasse 85 22607 Hamburg, Germany ___ 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 -- 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 ___ 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
[QE-users] question about last steps of vc-relax
Dear All, I was playing with one structure 'vc-relax', tested that it converged to the pressure I was aiming for. If I understand correctly, after structural relaxation QE (e.g. step 1) runs an additional 'scf' run (step 2) and recalculates stuff and in both steps recalculates pressure. It is interesting that at a single low pressure point, the pressure shown in 1 - is very close to 2, while in higher pressure points the last step shows lower pressure than 1 by some GPa. An example - target relaxation pressure 600 kbar: 1 - total stress (Ry/bohr**3) (kbar) P= 600.65 - last run of structure relaxation 2 - total stress (Ry/bohr**3) (kbar) P= 484.28 - final scf run May I ask - what does it indicate, which value I should trust more and how should I proceed? Is it because of this? SCF correction compared to forces is large: reduce conv_thr to get better values For me it is conv_thr = 6.40d-06 Thank you! best wishes, Konstantin -- Beamline Scientist DESY, FS-PE, bldg. 47c, L115 Notkestrasse 85 22607 Hamburg, Germany ___ 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
