[Wannier] spin information of Wannier functions

[Chong Wang]

Hi Shu-Ting and everyone else:


I think I figured out what happened.


If we do not use spinor feature in wannier90 but include spin orbit coupling in ab initio calculations, Steepest-descent minimization does not mix spin up and spin down. Thus, the orbitals keep their spin information. For vasp, it is first half up, second half down; for quantum espresso, it is odd up, even down.


Best!


Chong

________________________________
From: Wannier <wannier-bounces at quantum-espresso.org> on behalf of Chong Wang <ch-wang at outlook.com>
Sent: Friday, March 24, 2017 10:34:57 AM
To: Shu-Ting Pi
Cc: wannier at quantum-espresso.org
Subject: Re: [Wannier] spin information of Wannier functions


Hi Shu-Ting,


Here's an output example:


  WF centre and spread    1  (  0.000003,  1.907315,  7.573554 )     1.90180781
  WF centre and spread    2  (  0.000009,  1.957394,  7.573599 )     2.18257344
  WF centre and spread    3  ( -0.000006,  1.874192,  7.573602 )     2.17989134
  WF centre and spread    4  (  0.000016,  2.066193,  7.573556 )     2.11466608
  WF centre and spread    5  ( -0.000007,  1.776180,  7.573554 )     2.12950677
  WF centre and spread    6  (  0.000070, -0.021664,  9.431685 )     2.06812234
  WF centre and spread    7  ( -0.000054, -0.014828,  9.236149 )     2.16741854
  WF centre and spread    8  ( -0.000000,  0.035818,  9.238267 )     2.16653129
  WF centre and spread    9  (  0.000005, -0.021648,  5.715520 )     2.06808173
  WF centre and spread   10  ( -0.000012, -0.014840,  5.911021 )     2.16732828
  WF centre and spread   11  (  0.000001,  0.035807,  5.908902 )     2.16651165
  WF centre and spread   12  (  0.000017,  1.907317,  7.573556 )     1.90176869
  WF centre and spread   13  ( -0.000005,  1.957394,  7.573599 )     2.18256299
  WF centre and spread   14  (  0.000001,  1.874187,  7.573597 )     2.17988107
  WF centre and spread   15  (  0.000041,  2.066188,  7.573565 )     2.11463312
  WF centre and spread   16  ( -0.000049,  1.776183,  7.573547 )     2.12949448
  WF centre and spread   17  ( -0.000012, -0.021646,  9.431696 )     2.06811215
  WF centre and spread   18  (  0.000014, -0.014842,  9.236153 )     2.16738956
  WF centre and spread   19  ( -0.000000,  0.035808,  9.238272 )     2.16654910
  WF centre and spread   20  (  0.000064, -0.021570,  5.715492 )     2.06802554
  WF centre and spread   21  ( -0.000057, -0.014845,  5.911027 )     2.16728596
  WF centre and spread   22  (  0.000003,  0.035764,  5.908914 )     2.16648206

>From WF center and spread, It seems to be first half up and second half down.


Also, since you said you did a lot of test, does the spin information extracted from .spin file agree with some simple rule like "odd for up, even for down"?


Best.


Chong

________________________________
From: Shu-Ting Pi <pipidog at gmail.com>
Sent: Friday, March 24, 2017 9:25:17 AM
To: Chong Wang
Cc: wannier at quantum-espresso.org
Subject: Re: [Wannier] spin information of Wannier functions

Hello,

"And first half of the Wannier functions are spin up while second half are spin down."
I'm pretty sure it is a wrong statement ! I did a lot test and I don't think it works.

In some cases, spin up and down can be identified by time-reversal symmetry in SOC calculation.
However, even if it works, they are usually arranged as "odd for up, even for down".

Actually, in most cases, you cannot extract any information about spin without .spn file.

Best,
Shu-Ting

On Thu, Mar 23, 2017 at 6:04 PM, Chong Wang <ch-wang at outlook.com<mailto:ch-wang at outlook.com>> wrote:

Hi,


I am told that in the presence of spin-orbit coupling, the Wannier functions generated by Wannier90 package are eigenstates of s_z (spin operator in the z direction), even without a .spn input file. And first half of the Wannier functions are spin up while second half are spin down.


As far as I am concerned, Wannier90 package does not know anything about spin if .spn files are not present. Then why Wannier functions should end up to be eigenstates of s_z?


Chong Wang

Institute of Advanced Study, Tsinghua University

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