[Wannier] understanding the output of Wannier90

[Gianluca Giovannetti]

Dear Young-Su,

thank you for your replay.

if i take the previous unit cell:

----->a
| o     o | o     o|

 A1   B1 A2  B2

   2    1   2    1

the first wannier function is located to B1 and the second one is located to
A2.
this information i was missing to report/say in my previous email.

Following your suggestion then:

    0    0    0    2    1    0.222025    0.000000
    0    0    0    1    2    0.222025    0.000000

is meaning that hopping between B1 and A2 is 0.222025;

    1    0    0    2    1    0.203502    0.000000

is meaning that hopping between A2 and B2 is 0.203502;

  -1    0    0    1    2    0.203502    0.00000

is meaning that hopping between B1 and A1 is 0.203502

This makes sense to me.

cheers,

Gianluca Giovannetti






2011/3/7 Young-Su Lee <lee0su at kist.re.kr>

> Dear Gianluca Giovannetti,
>
>
>
> You can interpret hr.dat using the five indices preceding the H matrix
> element:
>
>   i j k m n  indicates H element between the m_th WF at the final center
> and the n_th WF at (the final center + (i,j,k) lattice vector) – please
> someone correct me, if this is wrong.
>
>
>
> The WF indices follow the order in the *wout file.
>
> The final center does not have to reside in the home cell, as you’ve
> already noticed from the WF at A2.
>
> If your first WF is at A2 and the second one is at B1
>
>
>
> 1 0 0 2 1 : btw B1 and A3
>
> 1 0 0 1 2 : btw A2 and B2
>
> -1 0 0 2 1 : btw B1 and A1
>
>
>
> If you want to move the WF at A2 to A1, use translation_centre_frac = 0.5,
> 0.5, 0.5, then all the WFs will be inside your home cell
> (translate_home_cell only translates centers without modifying hr.dat). I
> guess this is less confusing.
>
>
>
> Hope this helps.
>
>
>
> Young-Su
>
>
>
>
>
> * ----- Original Message -----*
> From: Gianluca Giovannetti
> To: wannier at quantum-espresso.org
> Date: 2011-03-07 17:15:40
> Subject: [Wannier] understanding the output of Wannier90
> Dear All,
>
> i`m having a problem in understanding the output of wannier90 (file hr
> .dat).
>
> i have made a calculation for a molecular crystal.
>
> the unit cell consists of molecular sites (A and B) along the stacking
> direction a (with a lattice vector) as illustrated in the following:
>
> -----> a
>
> |o ? o | o ? o | ......
> ?A ? B ?A ?B
>
> (here i`m plotting schematically two unit cells)
>
> Let label the molecules in this way:
>
>  -----> a
>
> |o ? ?o | o ? ?o | ......
> ?A1 B1 A2 B2
>
> now the bonds B1-A2 are shorter while bonds A2-B2 are longer (the system is
> dimerized).
>
> the HOMOs (highest occupied molecular orbitals) of the two molecules A,B
> contained in the unit cell hybridize, giving rise to bonding and
> antinbonding bands around the Fermi level. then at Fermi level i have two
> states.
>
> the calculations performed with PW and W90 looks fine and the agreement of
> PW and W90 bands is good.
>
> once i plot using xcrystalden the Wannier functions of the such states at
> Fermi one is located at A2 and the other one is located to B1 (basically one
> is in the unit cell and the other one is located at the NN unit cell along
> a).
>
> now i go to look at the hr.dat file and i find:
>
> ??? 0 ? ?0 ? ?0 ? ?1 ? ?1 ? ?3.334228 ? ?0.000000
> ?? ?0 ? ?0 ? ?0 ? ?2 ? ?1 ? ?0.222024 ? ?0.000000
> ?? ?0 ? ?0 ? ?0 ? ?1 ? ?2 ? ?0.222024 ? ?0.000000
> ?? ?0 ? ?0 ? ?0 ? ?2 ? ?2 ? ?3.334221 ? ?0.000000
>
>  ?? ?1 ? ?0 ? ?0 ? ?1 ? ?1 ? ?0.000243 ? ?0.000000
> ?? ?1 ? ?0 ? ?0 ? ?2 ? ?1 ? ?0.203498 ? ?0.000000
> ?? ?1 ? ?0 ? ?0 ? ?1 ? ?2 ? ?0.000122 ? ?0.000000
> ?? ?1 ? ?0 ? ?0 ? ?2 ? ?2 ? ?0.000242 ? ?0.000000
>
>  ?? -1 ? ?0 ? ?0 ? ?1 ? ?1 ? ?0.000243 ? ?0.000000
> ?? -1 ? ?0 ? ?0 ? ?2 ? ?1 ? ?0.000122 ? ?0.000000
> ?? -1 ? ?0 ? ?0 ? ?1 ? ?2 ? ?0.203498 ? ?0.000000
> ?? -1 ? ?0 ? ?0 ? ?2 ? ?2 ? ?0.000242 ? ?0..000000
>
> i have some doubts in understanding the hopping parameters.
>
> i see the kinetic terms are different?0.222024/0.203498 as one would expect
> in a dimerized structure. this is fine.
>
> the values 3.334228 are the on-site energies of the tight-binding problem.
>
> my problem is the following.
> is 0.222024 referring to the the hopping between A1 and B1 (also between A2
> and B2) ?or between B1 and A2?
>
> because the Wannier functions plotted in real space are sitting between
> adjacent different unit cells i would expect 0.222024 referring to?hopping
> between?B1 and A2 and 0.203498??referring to?hopping between?A1 and B1 (also
> between A2 and B2).
> then at smaller distances would correspond larger hoppings and at larger
> distances?would correspond smaller?hoppings.
>
> could you please confirm this way to interpret the file hr.dat? :-)
>
> i thank you in advance for our time.
>
> cheers,
>
> Gianluca Giovannetti
>
>
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