[QE-users] I'm confused about how to use PBE0

[Giuseppe Mattioli]

A 4-atom unit cell of ZnO can likely run on a desktop/laptop pc using  
PBE0, as long as you don't care too much about your hardware  
(desktop/laptop pc are generally not happy if you stress them for  
hours with codes designed mainly for workstation/HPC use). You can  
still find somewhere in the internet a famous video posted many years  
ago by prof. Marzari who run a 2-atom Si cell on his Nokia N-something  
cell phone. :-D

Completely different is the case of a ZnO bulk supercell or even  
surface slab. No way in this case, you need suitable resources.

Anyway, ZnO is a nasty beast, as you can have spurious mixing of Zn 3d  
and O 2p shells. If you are mainly interested in recovering a band gap  
close to the optically measured one, then you should mess with the EXX  
fraction of PBE0 (or HSE), raising it to 35-40%.

HTH
Giuseppe

Quoting Battal Malika <rose-marron2008 at hotmail.fr>:

> Dear Lorenzo,
>
> Sorry it's not a laptop but a desktop computer, would it be possible  
> in this case?
>
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> ----------------------------------------------------------------------------------------------------------------------------------------------------
> Malika battal
> student - Qatar University
>
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> ________________________________
> De : users <users-bounces at lists.quantum-espresso.org> de la part de  
> Lorenzo Paulatto <lorenzo.paulatto at cnrs.fr>
> Envoyé : mercredi 1 mars 2023 22:02
> À : users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
> Objet : Re: [QE-users] I'm confused about how to use PBE0
>
>
> Dear Malika,
>
> the Fock exchange (also known as exact exchange) included in PBE0 is  
> very computationally intensive, it is unlikely that you'll be able  
> to run it on a laptop.
>
> kind regards
>
>
> On 01/03/2023 22:30, Battal Malika wrote:
> Hello,
> I noticed that bandgap of ZnO is underestimated when using GGA. It  
> seems like PBE0 is the most accurate methode in my case to find a  
> value close to the experimental one. Neverthless I don't know how to  
> use it and how much time i'll need to run it in a laptop with 8  
> processors.
> Can you please clarify my doubts?
>
>
>
>
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------
> Malika battal
> student - Qatar University
>
>
>
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> Dr. Lorenzo Paulatto
> IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>