USPP, PW91 and PBE

Question on input files/tags, interpreting output, etc.

Please check whether the answer to your question is given in the VASP online manual or has been discussed in this forum previously!

Moderators: Global Moderator, Moderator

Post Reply
Message
Author
monty-wang
Newbie
Newbie
Posts: 6
Joined: Thu Jan 02, 2020 1:30 pm

USPP, PW91 and PBE

#1 Post by monty-wang » Wed Jan 06, 2021 2:32 pm

Dear Admit and All
Thank you very much for you kind help.
I recently have to use USPP to calculate a large system. However there is only uspp-gga-91 POTCAR but not uspp-gga-pbe files? Can GGA=PE in INCAR be set in order to use GGA-PBE XC? Because I heart that uspp can not be with PBE. I tried GGA=PE and worked, but the results are a little different from PW91.
Any response is appreciated.

martin.schlipf
Global Moderator
Global Moderator
Posts: 455
Joined: Fri Nov 08, 2019 7:18 am

Re: USPP, PW91 and PBE

#2 Post by martin.schlipf » Thu Jan 07, 2021 6:55 am

We recommend to use the PAW potentials even for large systems. Which version of VASP are you using?

alex
Hero Member
Hero Member
Posts: 567
Joined: Tue Nov 16, 2004 2:21 pm
License Nr.: 5-67
Location: Germany

Re: USPP, PW91 and PBE

#3 Post by alex » Thu Jan 07, 2021 8:29 am

Dear monty-wang,

PAW potentials provide higher accuracy at similar cost compared to USPP. That's why they are so successful and widely used. I'd strongly recommend to use them instead of USPPs.
If you want to learn about the differencies I'd like to point you to Georg's workshop contribution https://www.vasp.at/vasp-workshop/pseudopp2.pdf

Cheers,

alex

monty-wang
Newbie
Newbie
Posts: 6
Joined: Thu Jan 02, 2020 1:30 pm

Re: USPP, PW91 and PBE

#4 Post by monty-wang » Fri Jan 08, 2021 12:50 am

Dear Martin, Alex and All
Thank you very much. I am engaged in a large system with almost one thousand atoms and our supercomputer is powerfully limited . I know the accuracy of PAW and there are still some cases in which USPP is used.
So may I use the GGA=PE to set PBE with USPP?
Any response is appreciated.

martin.schlipf
Global Moderator
Global Moderator
Posts: 455
Joined: Fri Nov 08, 2019 7:18 am

Re: USPP, PW91 and PBE

#5 Post by martin.schlipf » Fri Jan 08, 2021 7:29 am

Well there are always some deficiencies when you change the xc potential. For PAW the system is flexible enough to deal with it so that it essentially amounts to just using a different core potential. I wouldn't recommend the same for USPP, though. Even for PAWs it is recommended that you use a PAW close to the desired functional, i.e. for a PBE0 calculation you would use the PBE PAW and not the LDA one.
To be completely honest, if your system size is such that being able to execute it depends on using USPPs over PAWs, it will be difficult to get reasonable results in either case. How would you study the convergence with respect to the energy cutoff ENCUT, which has typically a much larger computational cost associated with it?

monty-wang
Newbie
Newbie
Posts: 6
Joined: Thu Jan 02, 2020 1:30 pm

Re: USPP, PW91 and PBE

#6 Post by monty-wang » Mon Jan 11, 2021 7:40 am

martin.schlipf wrote: Thu Jan 07, 2021 6:55 am We recommend to use the PAW potentials even for large systems. Which version of VASP are you using?
Dear Prof. Martin
I use vasp5.3.5
Thank you very much

martin.schlipf
Global Moderator
Global Moderator
Posts: 455
Joined: Fri Nov 08, 2019 7:18 am

Re: USPP, PW91 and PBE

#7 Post by martin.schlipf » Mon Jan 11, 2021 8:03 am

Well your license also allows you to use VASP 5.4.4 and the PAW 54 potentials, so I'd recommend upgrading to those. Contact your PI who should have access to them.

monty-wang
Newbie
Newbie
Posts: 6
Joined: Thu Jan 02, 2020 1:30 pm

Re: USPP, PW91 and PBE

#8 Post by monty-wang » Wed Jan 13, 2021 1:10 am

Dear Prof. Martin
Thank you very much. We have checked the cutoff energy and it goes well. We will use USPP then.
Thank you very much.

monty-wang
Newbie
Newbie
Posts: 6
Joined: Thu Jan 02, 2020 1:30 pm

Re: USPP, PW91 and PBE

#9 Post by monty-wang » Sun Jan 31, 2021 12:33 am

Dear Prof. Martin, Prof. Alex and All
Thank you very much for your kind help. We ran into problems.
When using PAW to calculate the magnetic system (bulk bcc Fe as an example), turn on the spin polarization calculation ISPIN = 2, set LORBIT = 11 and the appropriate MAGMOM, the calculated single atom magnetic moment appears at the tail of OUTCAR, after the calculation is completed.
But when USPP is used to calculate the magnetic system, the same parameter settings, and finally the single-atom magnetic moment information at the tail of OUTCAR is all displayed as 0.
We have learned that LORBIT = 11 is not applicable to USPP, so we tested different LORBIT and RWIGS, and still did not get good results.
Any response is appreciated.

henrique_miranda
Global Moderator
Global Moderator
Posts: 414
Joined: Mon Nov 04, 2019 12:41 pm
Contact:

Re: USPP, PW91 and PBE

#10 Post by henrique_miranda » Mon Feb 01, 2021 10:31 am

The USPPs are not updated in a long time and we don't provide support for them.
Martin has suggested that you use the PAW 54 pseudopotentials.

Post Reply