[Wannier] Req. uniqueness of Maximally localized Wannier functions

[Soumyadeep]

Thank you very much professor. Normally I start with,

(1) default outer energy window (taken from DFT by W90 code),
(2) Efermi+-1 inner energy window
(3) projection of those states which have maximum DOS at Fermi level
(4) SCF like k-points mesh or 12x12x12 generated by kmesh.pl

Then iterate over different inner energy window to match DFT and 
interpolated band structure. Is there any smarter way to do this?

with many thanks and best regards
Soumyadeep

On 09-03-2020 20:01, Nicola Marzari wrote:
> Looks good to me, and in outer you want the wannier interpolated to be 
> smooth.
> 
> 			nicola
> 
> 
> On 09/03/2020 15:04, Soumyadeep wrote:
>> Thank you very much professor Marzari for an elaborate description. 
>> But for MLWF, I check only these
>> 
>> (1) DFT and wannier interpolated band structure must match in inner 
>> energy window
>> (2) final spread is low
>> (3) Img[h^R_ij] ~ 0
>> 
>> Is there any other factor I need to check?
>> 
>> Normally I work on Fe-based superconducting materials which is 
>> metallic in nature and also have entangled bands.
>> 
>> with best regards
>> Soumyadeep
>> 
>> 
>> On 09-03-2020 16:54, Nicola Marzari wrote:
>>> Hi Soumyadeep,
>>> 
>>> plenty of literature on this, but some cases are discussed in Sec III 
>>> of
>>> https://arxiv.org/abs/1909.00433
>>> 
>>> In a nutshell: for non-magnetic insulators, the localization
>>> functional on the occupied bands seems to have one (or multiple, by
>>> symmetries - think benzene) well defined global minimum - all others
>>> correspond to messed-up phase factors, give rise to meaningless WFs,
>>> and those are not real (i.e. they have an imaginary components). I
>>> cannot discount though that e.g. during a mol. dyn. simulations one
>>> could find discontinuous jumps in the MLWFs centers from one timestep
>>> to another.
>>> 
>>> For non-magnetic systems where you disentangle also the empty bands,
>>> you can have more subtle, complex effects (see discussion above). In
>>> that respect, it also dependes if we call maximally localized the
>>> global minimum only, or also other local minima where WFs are real 
>>> and
>>> look meaningful.
>>> 
>>> For magnetic system, we have less case studies, and in general there
>>> are already multiple local minima of the KS-DFT functional.
>>> 
>>> If anyone has experiences something different, welcome to mention it 
>>> here.
>>> 
>>>                 nicola
>>> 
>>> 
>>> On 09/03/2020 06:21, Soumyadeep wrote:
>>>> Dear All,
>>>> 
>>>>    I have a query, is Maximally localized Wannier functions are 
>>>> unique set of functions? I mean for a particular system only one set 
>>>> of MLWF is possible or it can be many set depending on other 
>>>> factors?
>>>> 
>>>>    Waiting eagerly for your reply.
>>>> 
>>>> with many thanks and best regards
>>>> Soumyadeep
>>>> -------------------------------------------------------------------
>>>> Soumyadeep Ghosh,
>>>> Senior Research Fellow,
>>>> Homi Bhabha National Institute (HBNI),
>>>> Raja Ramanna Centre for Advanced Technology, Indore, India-452013
>>>> Mob: (+91)9424664553
>>>> User Lab: 0731244-2580
>>>> Email: soumyadeepghosh35 at gmail.com, soumyadeep at rrcat.gov.in
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