[Wien] regarding k-mesh and tolf

[Xavier Rocquefelte]

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.rocquefelte at univ-rennes1.fr> wrote:
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