Here is a link towards a paper which treats such systems using GGA and
HSE06. Indeed, with GGA the band gap is nearly zero for some of them.
https://arxiv.org/pdf/1706.08674.pdf
The point is that it seems to me that it will not be too much
problematic although your band gap is zero if the bands are simply
touching at the Fermi level.
You must check your band structure first.
In the paper they show HSEO6 band structures which clearly confirm that
GGA+U or onsite-hybrid will not be useful.
One option for you could be to do band structure using GGA and
Full-hybrid (HSE06 or PBE0) to compare and discuss the differences. Then
if the difference is only band gap reduction, you could use GGA for the
phonons calculations. In addition, it will allow you to estimate the
residual forces using both GGA and hybrid, which will be one more
confirmation (or not) that GGA is sufficient for your system.
Cheers
Xavier
Le 27/01/2018 à 16:01, chin Sabsu a écrit :
Sir, it is A2BX6, x is halogen.
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On Sat, Jan 27, 2018 at 7:23 PM, Xavier Rocquefelte
<xavier.rocquefe...@univ-rennes1.fr> wrote:
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