[QE-users] Time difference between PBE and PBE0 - PBE0 too long (not finishing) ...

[pboulet]

Hello,

As I understand from my small experience, PBE0 (or hybrids in general) is not just a question of time but also of memory. So it is better to run these calculations on supercomputers.
From PBE to PBE0 requires 10 to 1000 times more CPU depending on the system. If for a given system you can use 250 k-points for a SCF calculation with a GGA, you will be limited to say 30-50 k-points (perhaps even less) with a hybrid.

If I am correct and if possible for you, I suggest you use the hybrid HSE functional, which is based on the range-separated Exx potential evaluation, as this may save you a lot of CPU time (I am not sure for the memory usage).

Best,
Pascal Boulet
—
Professor in computational materials - DEPARTMENT OF CHEMISTRY
University of Aix-Marseille - Avenue Escadrille Normandie Niemen - F-13013 Marseille - FRANCE
Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50
Email : pascal.boulet at univ-amu.fr <mailto:pascal.boulet at univ-amu.fr>



> Le 22 nov. 2020 à 10:32, Husak Michal <Michal.Husak at vscht.cz> a écrit :
> 
> I would like to ask what is the typical time difference between running PBE and
> 
> and the hybrid PBE0 ...
> 
> 
> Using CASTEP the PBE0 takes typically 200-1000 x more time than PBE ...
> 
> This is OK , I run CASTEP on a 1000 node supercomputer and work is done in a few
> 
> days typically ...
> 
> 
> I had run PBE and PBE0  scf on super simple system (Al generated by Material Cloud www, diamond generated by me) ...
> 
> I run in  MP mode on 4 core CPU system ...
> 
> PBE - 7.5 second
> 
> PBE0 - run 24 hours and not yet finished
> 
> 
> PBE0 on the target molecule (alanine) crashed immediately with segmentation failure ...
> 
> 
> Do I something wrong, is there some magic in setting hybrid functional or do i relay need a supercomputer ? I believed I can just add PBE0 request to tested PBE setup ...
> 
> Can anybody send me a working sample PBE0 calculation setup for small organic molecular crystal ?
> 
> 
> Michal Husak
> 
> UCT Prague
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