PBE GGA with SG 15 basis set Vs. HSE06

[amukhe13]

Greetings All,

I am using the PerdewBurke-Ernzerhof (PBE) parametrization of GGA with SG 15 basis set to calculate the electronic and phonon bandstructure of a crystal. While doing so it was mentioned to me that PBE is an unusual choice for simulating correct bandstructure. I understand that PBE GGA underestimates the bandgap and we need meta-GGA to predict the bandgap with more accuracy. 

"Even  more  confusing  is  the  choice  of  the  functional:  first  PBE  is mentioned, then the authors claim that they use meta-GGA to fix the energy gap problem.Since the calculations are performed for a crystal it is not entirely clear for what PBE was used." - This is the exact comment.

I have seen recent papers in well reputed Journals that have used PBE GGA to simulate bandstructure for crystals.

Can PBE-GGA with SG15 basis not be used for a crystal structure? How does it compare with something like a HSE06 ?

Thank you for your time and looking forward to your reply.

[Petr Khomyakov]

The band gap issue does not have much to do with the use of SG15 pseudopotentials. This is just about the use of  approximate density functionals such as GGA or LDA. The problem is well documented in hundreds of papers and has been discussed on this Forum many times as well, so please take a look at the literature.

The GGA-PBE functional can be used for studying many  properties of crystals, e.g., structural and mechanical properties as well as many other properties, including electronic ones . Regarding electronic properties, DFT-GGA or LDA is good enough for many metallic systems that have no energy gap in the electronic spectrum, and not strongly correlated. For semiconductors, the Kohn-Sham band gap would not coincide with the fundamental gap even for the exact density functional. This is why one has to go beyond the standard DFT, adopting other approaches such as MGGA or hybrid functional such as HSE06. Comparison between GGA and HSE06 are available in the literature as I have already mentioned.