MGGA basis set/exchange correlation

[Peraz]

Hi,

Woulld you please explain why no matter what we choose  in predefined functional,  exchange and correlation in vnl for MGGA the pseudopotential stays the same (LDA.PZ)?

Another question is that If I want to relax the structure before using the MGGA to get the bandstructure what type of pseudopotential you suggest to use? LDA.PZ or GGA PBE?

I was going to use GGA.PBE but I cannoft figure out how to change the MGGA pseudopotential to GGA.PBE

Thanks in advance,

Regards,

[Jess Wellendorff]

1) There exists no pseudopotential generated with the TB09 MGGA exchange-correlation functional, because it is not possible to compute the XC total-energy with that functional. Consequently, the MGGA cannot be used to generate a pseudopotential, and one must therefore use a pseudopotential generated with a different functional.

2) We have chosen to use LDA pseudopotentials for MGGA calculations by default, but you can in principle also use GGA potentials. I'm not sure how much of a difference it will make.

3) For geometry optimization prior to a MGGA calculation, we usually go for a GGA functional, e.g. PBE or PBEsol. The PBEsol (denoted "GGA.PBES" in ATK) will often give rather accurate lattice constants as compared to experiments.