[Wannier] Fwd: Extracting tight binding Parameters
Christopher Pashartis
cpashartis at gmail.com
Tue Jun 28 16:36:52 CEST 2016
Hi Jesse,
On Tue, Jun 28, 2016 at 3:15 AM, Jesse Vaitkus <jesse.vaitkus at rmit.edu.au>
wrote:
> Hello Christopher,
>
> a few things. Firstly, did you check that before truncating your
> interactions whether the band structure was reconstructed? This is a very
> important first step, if these are not recreated then you have bigger
> problems.
>
*The band structure before truncating the interactions was very close to
the DFT calculation, I'm simply using nearest neighbour interactions right
now so I can attempt to reproduce (as a first step) the band structure
generated by the wannier90 hamiltonian. I want to be sure I extract the
parameters (which judging by your response there seems to be no issue?)
right as well as my code works.*
Secondly, you have not reported the average spread of the WFs which is the
> metric used to work out how localised they are, if it exceeds the nearest
> neighbour distance then you likely need next nearest neighbour.
>
*Understanding what you are saying: to make my band structure as accurate
as possible what you are saying is that I should at least include the
spread of the WFs, that makes sense. I'll keep that in mind when
reproducing my full result. I would tell you what they are, but my
computing cluster is currently undergoing maintenance.*
Thirdly, you have not shown us which bands you wish to disentangle, if
> they're entangled you might need to finesse your frozen window.
>
> Fourthly, 2,8 and 3,8 don't necessarily need to be the same; 2,8 and 8,2
> and 3,8 and 8,3 need to be hermitian conjugates of each other and no, w90
> does not impose symmetry, something that I would so absolutely love.
>
*With regards to the 2,8 and 3,8 , how do I then know if the tight binding
factor is negative or positive?*
> Lastly, unfortunately the way in which w90 orders your wannier functions
> need not be how you want them ordered so what you call anion and cation
> might not be so (just check their output positions and then you'll know,
> assuming that you haven't already done this and I'm out of line).
>
*I did check this yes, but I will now remember it for sure :)*
> An 'easy way' to enforce your own personal ordering is to start a new run
> using the positions of the converged WFs you should be able to tell which
> atoms these correspond to and then use a strong guiding centre constraint.
>
> I hope my list has helped you. Best of luck.
>
> Cheers,
> Jesse Vaitkus
>
*Thank you for the kind response, and thank you additionally for covering
many of these topics for a new user.*
*Christopher Pashartis*
>
> On 28 June 2016 at 03:13, Christopher Pashartis <cpashartis at gmail.com>
> wrote:
>
>> Hello,
>>
>> I'm new to using wannier90 and I am trying to extract tight binding
>> parameters for use in my code. Unfortunately, I cannot seem to reproduce
>> the correct tight binding result that I get from my DFT code (not QE). If
>> someone can verify, point me to a proper example, or correct me it would be
>> greatly appreciated.
>>
>> I've reduced my Hamiltonian to nearest neighbour interactions only,
>> therefore, since I am using a zinc blende structure these are the
>> corresponding matrix elements I am interested in:
>>
>> 0 0 0 1 1 -4.324417 -0.000000
>> 0 0 0 2 1 0.000002 -0.000000
>> 0 0 0 3 1 -0.000000 0.000000
>> 0 0 0 4 1 -0.000001 0.000000
>> 0 0 0 5 1 -1.472555 0.000000
>> 0 0 0 6 1 -1.157538 0.000000
>> 0 0 0 7 1 1.157536 -0.000000
>> 0 0 0 8 1 1.157537 -0.000000
>> 0 0 0 1 2 0.000002 0.000000
>> 0 0 0 2 2 2.843276 -0.000000
>> 0 0 0 3 2 0.000000 -0.000000
>> 0 0 0 4 2 0.000000 0.000000
>> 0 0 0 5 2 1.067338 0.000000
>> 0 0 0 6 2 0.180666 0.000000
>> 0 0 0 7 2 -1.181808 -0.000000
>> 0 0 0 8 2 -1.181808 -0.000000
>> 0 0 0 1 3 -0.000000 -0.000000
>> 0 0 0 2 3 0.000000 0.000000
>> 0 0 0 3 3 2.843276 -0.000000
>> 0 0 0 4 3 0.000000 -0.000000
>> 0 0 0 5 3 -1.067337 -0.000000
>> 0 0 0 6 3 -1.181809 -0.000000
>> 0 0 0 7 3 0.180665 0.000000
>> 0 0 0 8 3 1.181808 0.000000
>> 0 0 0 1 4 -0.000001 -0.000000
>> 0 0 0 2 4 0.000000 -0.000000
>> 0 0 0 3 4 0.000000 0.000000
>> 0 0 0 4 4 2.843276 -0.000000
>> 0 0 0 5 4 -1.067337 -0.000000
>> 0 0 0 6 4 -1.181809 -0.000000
>> 0 0 0 7 4 1.181808 0.000000
>> 0 0 0 8 4 0.180665 0.000000
>> 0 0 0 1 5 -1.472555 -0.000000
>> 0 0 0 2 5 1.067338 -0.000000
>> 0 0 0 3 5 -1.067337 0.000000
>> 0 0 0 4 5 -1.067337 0.000000
>> 0 0 0 5 5 -8.772213 0.000000
>> 0 0 0 6 5 -0.000003 0.000000
>> 0 0 0 7 5 -0.000003 -0.000000
>> 0 0 0 8 5 -0.000003 -0.000000
>> 0 0 0 1 6 -1.157538 -0.000000
>> 0 0 0 2 6 0.180666 -0.000000
>> 0 0 0 3 6 -1.181809 0.000000
>> 0 0 0 4 6 -1.181809 0.000000
>> 0 0 0 5 6 -0.000003 -0.000000
>> 0 0 0 6 6 0.872588 0.000000
>> 0 0 0 7 6 0.000000 0.000000
>> 0 0 0 8 6 0.000000 -0.000000
>> 0 0 0 1 7 1.157536 0.000000
>> 0 0 0 2 7 -1.181808 0.000000
>> 0 0 0 3 7 0.180665 -0.000000
>> 0 0 0 4 7 1.181808 -0.000000
>> 0 0 0 5 7 -0.000003 0.000000
>> 0 0 0 6 7 0.000000 -0.000000
>> 0 0 0 7 7 0.872588 0.000000
>> 0 0 0 8 7 -0.000000 0.000000
>> 0 0 0 1 8 1.157537 0.000000
>> 0 0 0 2 8 -1.181808 0.000000
>> 0 0 0 3 8 1.181808 -0.000000
>> 0 0 0 4 8 0.180665 -0.000000
>> 0 0 0 5 8 -0.000003 0.000000
>> 0 0 0 6 8 0.000000 0.000000
>> 0 0 0 7 8 -0.000000 -0.000000
>> 0 0 0 8 8 0.872588 0.000000
>>
>> From my interpretation, the corresponding LCAO parameters would be:
>> E_sa E_sc E_pa E_pc ssSigma sapcSigma scpaSigma ppSigma ppPi
>> -8.77210 -4.32453 0.87263 2.84323 -1.47257 1.06736 1.15752 0.18067 1.1818
>>
>> Where c corresponds to the cation (in this case it should be the 1-4
>> functions) and a is the anion (5-8 functions).
>>
>> With regards to my parameters above, does Wannier90 already build in
>> symmetry operations? For example at (2,8) vs (3,8) these should be the same
>> value (+ or - not both) unless I'm misinterpreting what this file truly
>> presents, so which should it be?
>>
>> Any help would be greatly appreciated!
>>
>> Christopher Pashartis
>> Masters Candidate
>> McMaster University
>>
>>
>>
>>
>>
>> _______________________________________________
>> Wannier mailing list
>> Wannier at quantum-espresso.org
>> http://mailman.qe-forge.org/cgi-bin/mailman/listinfo/wannier
>>
>>
>
>
> --
>
> ————————————————————————————————
> Mr. Jesse Vaitkus MAIP
> BAppSc(Phys) Hons, BAppSc(Nano)
>
> PhD candidate
> Room 14.6.02
>
> Chemical and Quantum Physics
> School of Applied Sciences
> RMIT University
> Victoria 3001
> Australia
>
> jesse.vaitkus at rmit.edu.au
> ————————————————————————————————
>
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