[Wannier] Centre of Wannier functions

[李滕辉]

Dear Wannier90 developers:
I meet an issue while using Wannier90 v3.1.0, together with VASP v6.4.1. I've done some AIMD calculations to generate a continuous trajectory. Then I proceeded with Wannier analysis and subsequently examined the Hamiltonian. Within the input file, I have specified the atom centers, aiming to obtain WFs centered on these atom locations, or at least in close proximity to them.



...

Begin Projections

 Cd:sp3:z=-1,-1,-1,x=1,0,-1

 Se:p:z=-1,-1,-1,x=1,0,-1

End Projections

...

begin unit_cell_cart

     6.0500000     0.0000000     0.0000000

     0.0000000     6.0500000     0.0000000

     0.0000000     0.0000000     6.0500000

end unit_cell_cart

begin atoms_cart

Cd       1.5178271     1.7957993     1.4240287

Cd       4.4307325     4.4894561     1.7053815

Cd       4.5160066     1.2418392     4.5483831

Cd       1.5803075     4.4594387     4.5691762

Se       0.0050033     0.0332671     5.9680866

Se       6.0433290     3.0636897     3.0562890

Se       2.8807786     0.0724863     3.0164791

Se       3.2493695     3.0420933     5.8999131

end atoms_cart

...


However, I have observer that the WFs are not aligning with the atom centers of the home cell. Instead, they are centered on atoms within a unit cell whose center is located at(0.0, 0.0, 0.0). For instance,  since I use sp3orbitals for Cd, the center of WF5 corresponds to the second Cd atoms, while the atom center positioned at (4.43. 4.49. 1.71) and the WF center at (-1.01, -2.12, 1.14) in the .wout file.


...

 Final State

  WF centre and spread    1  (  2.085684,  1.260598,  0.798043 )     3.47876053

  WF centre and spread    2  (  2.049201,  2.344944,  1.921311 )     3.44168714

  WF centre and spread    3  (  0.904277,  1.241577,  1.954697 )     3.43610592

  WF centre and spread    4  (  1.042490,  2.326357,  0.905988 )     3.58232243

  WF centre and spread    5  ( -1.010143, -2.123145,  1.141211 )     3.49051492

  WF centre and spread    6  ( -1.128292, -0.972610,  2.258101 )     3.52243681

  WF centre and spread    7  ( -2.121837, -2.038340,  2.220324 )     3.46813098

  WF centre and spread    8  ( -2.218949, -1.012121,  1.103897 )     3.51827962

  WF centre and spread    9  ( -1.015362,  0.681962, -2.070276 )     3.60904653

  WF centre and spread   10  ( -0.890789,  1.882241, -0.973578 )     3.63289332

  WF centre and spread   11  ( -2.108611,  0.719542, -0.996879 )     3.46637567

  WF centre and spread   12  ( -2.115134,  1.897953, -2.162619 )     3.66683836

  WF centre and spread   13  (  2.150342, -2.128650, -2.068309 )     3.51187251

  WF centre and spread   14  (  2.156870, -1.008390, -0.926044 )     3.53284787

  WF centre and spread   15  (  1.050800, -2.157773, -0.945039 )     3.46859217

  WF centre and spread   16  (  0.958142, -1.003749, -2.060564 )     3.59315863

  WF centre and spread   17  (  0.037244,  0.001632, -0.049092 )     2.50422447

  WF centre and spread   18  (  0.015322,  0.080868, -0.134619 )     2.21017329

  WF centre and spread   19  ( -0.059586,  0.030045, -0.095360 )     2.28365022

  WF centre and spread   20  (  0.037435, -3.029794, -2.977580 )     2.46391151

  WF centre and spread   21  (  0.000015, -2.932250, -3.012771 )     2.31121349

  WF centre and spread   22  ( -0.056325, -2.986181, -2.999162 )     2.38773168

  WF centre and spread   23  (  2.893882,  0.030034,  3.037144 )     2.38000522

  WF centre and spread   24  (  2.928631,  0.123782,  2.984530 )     2.38126096

  WF centre and spread   25  (  2.821335,  0.075610,  3.032140 )     2.43241519

  WF centre and spread   26  ( -2.791587, -3.058092, -0.116545 )     2.45592149

  WF centre and spread   27  ( -2.744926, -2.945582, -0.212516 )     2.32087924

  WF centre and spread   28  ( -2.851460, -3.004112, -0.153946 )     2.45045905

  Sum of centres and spreads (  0.018668,-17.703645, -0.597512 )    85.00170923

...


While this discrepancy does not present an issue in static calculations, it becomes problematic in MD trajectories. For instance, When an atom moves from (0, 0, 0.49) to (0, 0, 0.51), the center shifts from (0, 0, 0.49) to (0, 0, -0.49), resulting in a discontinuity in the Hamiltonian non diagonal element indices.


I've made attempts to address this issue by adjusting parameters in the .win file, such as setting translate_home_cell = true, or explicitly setting the center of each orbital. But none of them works. It seems that the WF centres are predetermined in ab initial calculations. Therefore, I am reaching out to inquire if there exist specific parameters or solutions to solve this problem.


Thank you for your attention and assistance. 


Best regards,
Tenghui Li
Department of Chemistry, Zhejiang University, China
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