[Wannier] How to reduce neighbors for Hamiltonian in Wannier basis ? :: HR_PLOT

[nicolas poilvert]

Dear Martin,

You don't need to reduce the number of Wigner-Seitz
points in order to identify the nearest neighbors because
seedname_hr.dat contains all the necessary information
in order for you to extract those neighbors.
The format goes as follows

R1  R2  R3  m  n   Re(<wm|H|wn>)  Im(<wm|H|wn>)

where R1, R2, R3 are the integer coordinates of unit cell
R (in the bases of the direct lattice vectors a1, a2, a3)
with respect to the "home" cell (R=0).

So all you need to do is extract all the matrix elements
corresponding to the proper nearest neighbor cell R.
For example if you had a 1D system like a nanotube in the
z-direction, then you would probably want to extract the
matrix elements corresponding to R = 0  0  1.

You could of course reduce the number of k points in your
calculation such that only the nearest neighbor cells would
show up but then your calculation would most probably not
be very converged for the Wannier functions (not enough
k point sampling).

Nicolas

On Thu, Apr 7, 2011 at 7:17 AM, Martin Gmitra <martin.gmitra at gmail.com>wrote:

> Dear Wannier90 users,
>
> We are interested to compare Hamiltonian in Wannier basis with a
> simple tight-binding
> nearest-neighbors model. My question is -- how one can reduce number
> of Wigner-Seitz
> grid-points nrpts such that resulting Hamiltonian (seedname_hr.dat)
> includes nearest
> neighbors only?
>
> Second question I do have is -- what are the units of the Hamiltonian
> matrix elements
> in the seedname_hr.dat file?
>
> With Best regards,
> Martin Gmitra
> _______________________________________________
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> Wannier at quantum-espresso.org
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>



-- 
POILVERT Nicolas
PhD candidate,
Dpt of Materials Science and Engineering
Massachusetts Institute of Technology
77, Massachusetts avenue
Cambridge, MA 02139
USA
work: (617) 452-4212
nicolas.poilvert at gmail.com
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