[QE-users] problem with convergence of MnTe altermagnet hexagonal phase

[Nicola Marzari]

Dear all,


just a note on these comments below. All codes (all electron, 
pseudopotential PAW, ultrasoft, normconserving) should give the same 
numerical result for a given physical approximation (e.g., PBEsol).

If they do not, there is a problem - this is why verification (in 
"verification and validation") is very important - making sure codes 
give a numerically exact answer to a given physical theory (the theory 
needs to be "validate", i.e. good enough to describe the physics at hand 
- you cannot do DFT PBEsol to study say a Hubbard sideband.

There has been a lot of progress on "verification", as you can see in 
https://www.nature.com/articles/s42254-023-00655-3 , with all-electron 
and pseudopotential codes giving very close restuls.

For QE, there are curated efforts here: 
https://legacy.materialscloud.org/discover/sssp/ - so that's a good 
start, and you can find PBE and PBEsol pseudos tuned for efficiency 
(lower cost) or accuracy (higher cost); we'll release very soon a major 
update with all the data from the paper above.

nicola


>     Authors of the paper used VASP but it should be possible in Quantum
>     Espresso.
> 
> 
> This is not always the case, do not assume this.
> Pseudopotentials are an important part of the calculation, which are 
> different sets for VASP and QE.
> The calculation and the code implementation are also different.
> 
-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, SNSF
Laboratory Head, PSI Center for Scientific Computing, Theory, and Data
Contact info and websites:  https://theos-wiki.epfl.ch/en/Main/Contact