[Wannier] Initial projection wannier centers (symmetry adapted wannier functions)

[Mostofi, Arash]

Dear Tobias,

In general you would need to apply constraints, either to the symmetry of the WFs (as in the work of Sakuma that you mention below), of by explicitly constraining the centres (as proposed in a recent paper by Marianetti et al, http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.165125). Unfortunately, neither approach is implemented in the main code at present.

Best wishes,

Arash

—
Arash Mostofi — www.mostofigroup.org<http://www.mostofigroup.org>
Reader in Theory and Simulation of Materials
Imperial College London
Director, Thomas Young Centre @Imperial

On 17 Dec 2015, at 14:31, Tobias Frank <pike.lucius at gmail.com<mailto:pike.lucius at gmail.com>> wrote:

Dear wannier90 users,

I currently try to wannierize MoS2, which has a disconnected band manifold of 11 bands (5 Mo d orbitals and 2*3 S p orbitals).

 *----------------------------------------------------------------------------*
 |   Site       Fractional Coordinate          Cartesian Coordinate (Ang)     |
 +----------------------------------------------------------------------------+
 | Mo   1   0.33333   0.66667   0.50000   |   -0.00000   1.84059  12.50000    |
 | S    1   0.66667   0.33333   0.56240   |    1.59400   0.92030  14.05992    |
 | S    2   0.66667   0.33333   0.43760   |    1.59400   0.92030  10.94008    |
 *----------------------------------------------------------------------------*

The goal is to get a symmetric tight-binding Hamiltonian (_hr.dat) out of the calculation. The scheme I use is to project onto atomic orbitals without any maximal localization iteration applied ("symmetry adapted wannier functions") and guiding centers are turned on.

My initial (and final) state reads:
projections:Mo:d, S:p

 Initial State
  WF centre and spread    1  ( -0.000000,  1.840629, 12.500000 )     1.65212451
  WF centre and spread    2  ( -0.000000,  1.797275, 12.500000 )     1.88788741
  WF centre and spread    3  ( -0.000000,  1.883825, 12.500000 )     1.88514896
  WF centre and spread    4  ( -0.000000,  1.744405, 12.500000 )     1.79754077
  WF centre and spread    5  ( -0.000000,  1.936664, 12.500000 )     1.79758431
  WF centre and spread    6  (  1.594000,  0.920313, 14.121223 )     1.69614206
  WF centre and spread    7  (  1.594000,  0.932663, 14.015563 )     1.56344882
  WF centre and spread    8  (  1.594000,  0.908001, 14.015556 )     1.56201127
  WF centre and spread    9  (  1.594000,  0.920313, 10.878777 )     1.69614206
  WF centre and spread   10  (  1.594000,  0.932663, 10.984437 )     1.56344882
  WF centre and spread   11  (  1.594000,  0.908001, 10.984444 )     1.56201127
  Sum of centres and spreads (  9.564000, 14.724751,137.500000 )    18.66349025

This yields a very good description of the band structure, but why are the initial projections not exactly at the atomic sites, where I specified them to be? This slight asymmetry reflects also in the tight-binding matrix elements, where I would like to have symmetric ones. Could you give me a hint how to get the wannier centers at the atomic positions?

I am aware about the publication of Sakuma ("Symmetry-adapted Wannier functions in the maximal localization procedure"). I am using Quantum Espresso, where it is not implemented. Is there any work on the way?

Thank you very much,
Tobias Frank
PhD student
Universität Regensburg
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