[Wien] Requesting gentle clarification on OMP_NUM_THREADS, run_lapw, volume optimisation and wien2k update.

Tue Jun 20 09:18:56 CEST 2023

Dear Peter and Laurence,

Thank you for your valuable inputs. I have some followup queries.

  1.  In the attached CIF file, I want to do DFT simulation on two situations. One when there is excess oxygen and one in less oxygen. However, I am confused as which part of the cif file I should modify/implement the changes
     *   If I add a new line and add more oxygen, I am unsure of what I should set in other parameters such as label, occupancy, fract_x,y,z etc.
     *   I am also confused on how many additions/removal can be considered as significant addition/reduction.
  2.  When I am adding/subtracting oxygen, for realistic results (matching simulation with lab experimental data), I should be doing the simulations on a large supercell or unit cell (for oxygen vacancies, I know that I should do a supercell as I cannot create it in the unit cell cif file)?
Once again, thank you so much for your continuous support to the community.

With warm regards,
Pranjal

From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> On Behalf Of Peter Blaha
Sent: Thursday, June 15, 2023 5:11 PM
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] Requesting gentle clarification on OMP_NUM_THREADS, run_lapw, volume optimisation and wien2k update.

In addition to what L. Marks has already said:

A unit cell with 216 atoms should be run in mpi parallel mode. You won't have too many k-points probably, in particularly when doing position optimization.

About OMP Laurence Marks has already answered. The Intel mkl does not scale to higher OMP numbers. But: Test it out yourself. Set OMP_NUM_TREADS to 1 and run one iteration. Check the dayfile how long it takes. Set it to 2,4,8,16 and check the timing .... You should see that lapw0 will benefit when you set it to 64 (for your 216 atom cell), but unfortunately not much speedup in lapw1/2 anymore.

Update of WIEN2k: You should install wien2k into a new directory, thus you do not destroy the old installation. In addition, there is a "copy" function in siteconfig which would copy the old settings to the new installation. It is briefly described on the download page .and in the (new !) usersguide as well as in the "update" site of wien2k.

Updating is strongly recommended since the new init_lapw has some automatic precision settings and you won't run your supercell with 1000 k-points .....

Volume optimization for high vacancy concentration is ok. What you read in the UG concerns the stress tensor, which is only NREL.

Hf-4f: No, these are core/semicore states. You don't need onsite-hybrid or LDA+U. However, depending on your RMTs you may be able to put them into the core by specifying a charge criterium instead of an energy (like   init -ecut 0.999)

I have some general queries and it would be great if you can kindly provide me your feedback.

  1.  I have 64 CPU (32 x 2) and more than 9 TB space and the system is dedicated entirely to do simulations on DFT. I was thinking to set the OMP_NUM_THREADS at 40 or 50 (even higher) to use the maximum potential of the computer. But in the guidebook, it is recommended that I do not set it higher than 8. May I please the reason for this recommendation?

  2.  Is there a code to run_lapw continuously till it reaches the convergence and not start it again after 40 cycles?

  3.  If I do a volume optimization for a single unit cell and then I create a supercell of the optimized structure. Does the supercell remains in optimized volume condition? Or it is recommended that I do a volume optimization for the supercell as well. Further is WIEN2k a reliable platform for volume optimization of HfO as in the guidebook on page 87 it mentions “The accuracy is thus limited to first and second row elements (maybe early 3d elements) and in particular for the 5d series and above, large errors may occur due to the neglect of (scalar-) relativistic corrections.”

  4.  Lastly, as it says on the website that it is highly recommended to update the WIEN2K version, I am unable to find the manual where I can follow the instructions to update the version. As I have not done any installation of WIEN2K (my past colleague installed the present version), I am worried that while upgrading I may commit some mistake. A guideline on updating would have been very helpful.

Looking forward to your kind feedback.

Thank you in advance.

With warm regards,
Pranjal

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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna

Phone: +43-158801165300

Email: peter.blaha at tuwien.ac.at<mailto:peter.blaha at tuwien.ac.at>

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Aquest missatge, i els fitxers adjunts que hi pugui haver, pot contenir informació confidencial o protegida legalment i s’adreça exclusivament a la persona o entitat destinatària. Si no consteu com a destinatari final o no teniu l’encàrrec de rebre’l, no esteu autoritzat a llegir-lo, retenir-lo, modificar-lo, distribuir-lo, copiar-lo ni a revelar-ne el contingut. Si l’heu rebut per error, informeu-ne el remitent i elimineu del sistema tant el missatge com els fitxers adjunts que hi pugui haver.

Este mensaje, y los ficheros adjuntos que pueda incluir, puede contener información confidencial o legalmente protegida y está exclusivamente dirigido a la persona o entidad destinataria. Si usted no consta como destinatario final ni es la persona encargada de recibirlo, no está autorizado a leerlo, retenerlo, modificarlo, distribuirlo o copiarlo, ni a revelar su contenido. Si lo ha recibido por error, informe de ello al remitente y elimine del sistema tanto el mensaje como los ficheros adjuntos que pueda contener.

This email message and any attachments it carries may contain confidential or legally protected material and are intended solely for the individual or organization to whom they are addressed. If you are not the intended recipient of this message or the person responsible for processing it, then you are not authorized to read, save, modify, send, copy or disclose any part of it. If you have received the message by mistake, please inform the sender of this and eliminate the message and any attachments it carries from your account.
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