[Wannier] the MLWFs of graphene

[Jonathan Yates]

Dear Janyang Xi,

 Giovanni is perfectly correct about bands outside the frozen window not necessarily being well reproduced. However, graphene/graphite is an interesting case - and if you set the windows correctly the 5 MLWF will pick out the sigma and pi bands exactly.
 See Section II.I.2 
of http://arxiv.org/abs/1112.5411
And also the wannier90 tutorial.

My guess is that you need to increase the outer window so that it includes the 8th band at gamma (the reason should be clear from a band structure plot) - maybe 12-13 eV? The pre-print listed above gives a detailed explanation of the two windows, 'outer' and 'frozen', used in the disentanglement procedure.

Yours
 Jonathan


On 5 Jul 2012, at 09:11, Giovanni Pizzi wrote:

> Dear Janyang Xi, 
> what do you mean with 'The 5th band of graphene along Gamma-K-M-Gamma is unsatisfactory compared with pwscf calculation'?
> 
> In your calculation, you set the frozen window to 3eV; you cannot thus expect that the bands at higher energy resemble the ab-initio calculated ones. Note also that for most purposes, one is only interested at what happens near the Fermi energy. So as far as the bands near the Fermi energy (and possibly a few eV above it) are correctly reproduced, the results shouldn't be affected.
> 
> If instead the bands are not correctly reproduced below 3eV, it is possible that you didn't reach convergence yet, or that you found a local minimum for the spread instead of the global minimum. 
> 
> Best,
> Giovanni Pizzi
> 
> 
> 
> On 07/05/2012 09:02 AM, 奚晋扬 wrote:
>> Dear all,
>>     I've just used the wannier90 code with the pwscf interface to calculate the electronic structure of graphene for practice.But I have some problems:
>>     I use 5 MLWFs for a primitive unit cell of graphene:  pz orbitals on every atom and sp2 orbitals on 'every other' atom. But the final spread(Ang^2) is still large(about 6.86). The 5th band of graphene along Gamma-K-M-Gamma is unsatisfactory compared with pwscf calculation.
>>     The inputs: xx.scf,xx.nscf,xx.pw2wan and xx.win; The outputs:xx.wout and band.JPG are in the attachments.
>>     Thanke you!
>>     Best wishes
>> 
>>   Jinyang Xi
>> 
>> 
>> 
>> 
>> 
>> 
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> 
> 
> -- 
> Giovanni Pizzi
> Post-doctoral Research Scientist
> EPFL STI IMX THEOS
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