[Wannier] unit cell and formula unit

[Jonathan Yates]

Dear Young-Joon,

 The AHC is reported in units of (Ohm cm)^-1 - it is a bulk property. So it should not matter if you study one unit cell, or 10, or 1000 unit cells, you should get the same answer. The fact that you get the same answer for the rhombohedral and hexagonal representations of the same crystal is a actually a nice validation of the method…
 By contrast, properties such as the orbital magnetisation are extensive (e.g. postw90 reports a magnetisation per unit cell)

 Jonathan
 

> On 11 Jul 2017, at 03:07, Young-Joon Song <blueway39 at korea.ac.kr> wrote:
> 
> Dear users and developers
> 
>  
> 
> Hello.
> 
>  
> 
> I’d like to ask a question related to the unit cell used in the Wannier90 code. Recently, I study on rhombohedral structure system.
> 
> This structure can transform to hexagonal one. In my case, the difference of formula unit between rhombohedral cell and hexagonal cell is three times.
> 
> After DFT calculation using WIEN2K code, I got MLWFs of both cases separately. Then I calculated the anomalous Hall conductivity with ‘postw90.x’.
> 
> Here is my question. Why are these values of the anomalous Hall conductivity similar in both cases of rhombohedral cell and hexagonal cell even their formula units are not same.
> 
> I think these values should be different by three times.
> 
>  
> 
> Any comment is very helpful for me.
> 
>  
> 
> Thank you in advance.
> 
> 
> Young-Joon Song
> 
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