From brad.malone at gmail.com  Wed May  2 21:42:32 2007
From: brad.malone at gmail.com (Brad Malone)
Date: Wed, 2 May 2007 12:42:32 -0700
Subject: [Wannier] Accuracy of fermi surface plot
Message-ID: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com>

Hi, I was wondering how accurate the eigenvalues given in the .BXSF file
when outputting the fermi surface are.  Does increasing the number  of
iterations (num_iter) increase the accuracy, or does this number only affect
the Wannierization?


Thanks,
Brad
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From jry20 at cam.ac.uk  Wed May  2 22:22:21 2007
From: jry20 at cam.ac.uk (Jonathan Yates)
Date: Wed, 2 May 2007 21:22:21 +0100 (BST)
Subject: [Wannier] Accuracy of fermi surface plot
In-Reply-To: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com>
References: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com>
Message-ID: <Pine.LNX.4.63.0705022059440.17271@tcmpc44.phy.cam.ac.uk>

On Wed, 2 May 2007, Brad Malone wrote:

> Hi, I was wondering how accurate the eigenvalues given in the .BXSF file
> when outputting the fermi surface are.  Does increasing the number  of
> iterations (num_iter) increase the accuracy, or does this number only affect
> the Wannierization?

Brad,

  num_iter sets the maximum number of steps to take when minimising the 
spread of the Wannier functions. If you set this to a small number you may 
find that the spread of the WF is converged to only, say, 1x10-6 Ang^2, 
rather than machine precision.

  However, this should have no significant effect on the quality of the 
interpolated eigenvalues.[*] The Wannier interpolation procedure requires 
having well localised WF, rather than maximally localised WF (ie it 
doesn't matter if you're not at the exact minimum of the spread).

  The quality of the interpolated eigenvalues is determined by the spacing 
of the ab-initio k-point mesh used to compute the WF. In fact the quality 
of the interpolation increases exponentially with the spacing of this 
mesh.(denser k-grid => better interpolation). See cond-mat/0702554 
particularly the Appendix (this will appear in PRB shortly)

  In order for you to assess the quality of the interpolation I suggest the 
following procedure:

  Plot a band structure along various high symmetry directions using 
Wannier90.
  Plot an equivalent band-structure using your ab-initio code. Note: if 
you're using pwscf, Wannier90 will write a file <seedname>_band.kpt, which 
contains the path kpoints in pwscf format.
  Compare the two band-structures.
  Increase the density of the k-point mesh used to compute the WF until the 
interpolated bands have an accuracy sufficient for your needs.

  Yours
    Jonathan


[*] Of course this is a simple thing to check out numerically - so you 
don't have to take my word for it.

-- 
Dr Jonathan Yates         |    Theory of Condensed Matter Group
Corpus Christi College    |    Cavendish Laboratory
Cambridge, CB2 1RH, UK    |    Cambridge, CB3 OHE, UK
email jry20 at cam.ac.uk     |    Tel +44 (0)1223 337461



From ogitsu at llnl.gov  Sat May  5 02:34:55 2007
From: ogitsu at llnl.gov (Tadashi Ogitsu)
Date: Fri, 4 May 2007 17:34:55 -0700
Subject: [Wannier] a little problem with pwscf 3.2.1?
In-Reply-To: <Pine.LNX.4.63.0705022059440.17271@tcmpc44.phy.cam.ac.uk>
References: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com> <Pine.LNX.4.63.0705022059440.17271@tcmpc44.phy.cam.ac.uk>
Message-ID: <EC0BE892-B57E-44D2-8F95-814019B8C49A@llnl.gov>

Hi Wannier90s,

I've found a small problem with, I think, pw2wannier90 came with  
pwscf3.2.1 (3.2 plus the distributed patch on their wabpage).

Somewhat they have changed the output format of .eig file so that the  
last data, the weight of each eigenvalues, does not exist anymore,  
while the current distribution of wannier90 try to read and complains  
that the data is not consistent.

I just removed the last read as follows,

old:
read(eig_unit,*,err=106,end=106) i,j,eigval(n,k),wg(n,k)
new:
read(eig_unit,*,err=106,end=106) i,j,eigval(n,k)

First of all, is my understanding correct? (i.e., this is a problem  
caused by the change in pw2wannier90 in 3.2.1 distribution)

Second, did I do the right correction? (I have no idea if wg is used  
anywhere, although it does not seem to be...)

Thanking in advance!

Tadashi
PS. Jonathan, I've started to work on the gold transport and as the  
first try, I'm playing with the example6.


From mostofi at MIT.EDU  Sat May  5 04:18:43 2007
From: mostofi at MIT.EDU (Arash A Mostofi)
Date: Fri, 4 May 2007 22:18:43 -0400 (EDT)
Subject: [Wannier] a little problem with pwscf 3.2.1?
In-Reply-To: <EC0BE892-B57E-44D2-8F95-814019B8C49A@llnl.gov>
References: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com>
 <Pine.LNX.4.63.0705022059440.17271@tcmpc44.phy.cam.ac.uk>
 <EC0BE892-B57E-44D2-8F95-814019B8C49A@llnl.gov>
Message-ID: <Pine.GSO.4.64L.0705042150500.15236@department-of-alchemy.mit.edu>

Dear Tadashi

I'm slightly confused: the eigenvalues have always (ie, since the original 
incarnation of pw2wannier90 in December 2005) been written by pw2wannier90 
as:

   write (iun_band,'(2i5,f18.12)') ibnd1, ikevc, et(ibnd,ik)*rytoev

(ie, without any reference to weights, wg). This is easily verified by 
checking the espresso cvs repository.

Consequently, Wannier90 has always read the eigenvalues as:

    read(eig_unit,*,err=106,end=106) i,j,eigval(n,k)

as I've verified by checking our Wannier90 cvs repository.

Can you remember from where you got your copy of the Wannier90 source? Was 
it from the www.wannier.org or from someone who may have made some 
modifications for his/her own purposes? In any case, the change you've 
made is correct.

Best regards

Arash

-----------------------------------------
Dr Arash A Mostofi
Dept of Materials Science and Engineering
13-4084 MIT
77 Massachusetts Avenue
Cambridge MA 02139-4307 USA
Tel: 617.2536026
-----------------------------------------

On Fri, 4 May 2007, Tadashi Ogitsu wrote:

> Hi Wannier90s,
>
> I've found a small problem with, I think, pw2wannier90 came with 
> pwscf3.2.1 (3.2 plus the distributed patch on their wabpage).
>
> Somewhat they have changed the output format of .eig file so that the 
> last data, the weight of each eigenvalues, does not exist anymore, while 
> the current distribution of wannier90 try to read and complains that the 
> data is not consistent.
>
> I just removed the last read as follows,
>
> old:
> read(eig_unit,*,err=106,end=106) i,j,eigval(n,k),wg(n,k)
> new:
> read(eig_unit,*,err=106,end=106) i,j,eigval(n,k)
>
> First of all, is my understanding correct? (i.e., this is a problem 
> caused by the change in pw2wannier90 in 3.2.1 distribution)
>
> Second, did I do the right correction? (I have no idea if wg is used 
> anywhere, although it does not seem to be...)
>
> Thanking in advance!
>
> Tadashi
> PS. Jonathan, I've started to work on the gold transport and as the first 
> try, I'm playing with the example6.
> _______________________________________________
> Wannier mailing list
> Wannier at quantum-espresso.org
> http://www.democritos.it/mailman/listinfo/wannier


From ogitsu at llnl.gov  Mon May  7 20:13:44 2007
From: ogitsu at llnl.gov (Tadashi Ogitsu)
Date: Mon, 7 May 2007 11:13:44 -0700
Subject: [Wannier] a little problem with pwscf 3.2.1?
In-Reply-To: <Pine.GSO.4.64L.0705042150500.15236@department-of-alchemy.mit.edu>
References: <bf16929a0705021242j7b5fde5fv9d972f68d7456c37@mail.gmail.com> <Pine.LNX.4.63.0705022059440.17271@tcmpc44.phy.cam.ac.uk> <EC0BE892-B57E-44D2-8F95-814019B8C49A@llnl.gov> <Pine.GSO.4.64L.0705042150500.15236@department-of-alchemy.mit.edu>
Message-ID: <34D087AF-F363-4BC6-8A54-92218C68A490@llnl.gov>

Hi Arash,

Thanks for the response. Well, then, I got a non-official version  
probably...? I thought, I downloaded from the webpage, but I cannot  
be 100% sure.

I'll download the official distribution and replace with the one I  
have now just in case. Sorry about the confusion.

Tadashi
On May 4, 2007, at 7:18 PM, Arash A Mostofi wrote:

> Dear Tadashi
>
> I'm slightly confused: the eigenvalues have always (ie, since the  
> original incarnation of pw2wannier90 in December 2005) been written  
> by pw2wannier90 as:
>
>   write (iun_band,'(2i5,f18.12)') ibnd1, ikevc, et(ibnd,ik)*rytoev
>
> (ie, without any reference to weights, wg). This is easily verified  
> by checking the espresso cvs repository.
>
> Consequently, Wannier90 has always read the eigenvalues as:
>
>    read(eig_unit,*,err=106,end=106) i,j,eigval(n,k)
>
> as I've verified by checking our Wannier90 cvs repository.
>
> Can you remember from where you got your copy of the Wannier90  
> source? Was it from the www.wannier.org or from someone who may  
> have made some modifications for his/her own purposes? In any case,  
> the change you've made is correct.
>
> Best regards
>
> Arash
>
> -----------------------------------------
> Dr Arash A Mostofi
> Dept of Materials Science and Engineering
> 13-4084 MIT
> 77 Massachusetts Avenue
> Cambridge MA 02139-4307 USA
> Tel: 617.2536026
> -----------------------------------------
>
> On Fri, 4 May 2007, Tadashi Ogitsu wrote:
>
>> Hi Wannier90s,
>>
>> I've found a small problem with, I think, pw2wannier90 came with  
>> pwscf3.2.1 (3.2 plus the distributed patch on their wabpage).
>>
>> Somewhat they have changed the output format of .eig file so that  
>> the last data, the weight of each eigenvalues, does not exist  
>> anymore, while the current distribution of wannier90 try to read  
>> and complains that the data is not consistent.
>>
>> I just removed the last read as follows,
>>
>> old:
>> read(eig_unit,*,err=106,end=106) i,j,eigval(n,k),wg(n,k)
>> new:
>> read(eig_unit,*,err=106,end=106) i,j,eigval(n,k)
>>
>> First of all, is my understanding correct? (i.e., this is a  
>> problem caused by the change in pw2wannier90 in 3.2.1 distribution)
>>
>> Second, did I do the right correction? (I have no idea if wg is  
>> used anywhere, although it does not seem to be...)
>>
>> Thanking in advance!
>>
>> Tadashi
>> PS. Jonathan, I've started to work on the gold transport and as  
>> the first try, I'm playing with the example6.
>> _______________________________________________
>> Wannier mailing list
>> Wannier at quantum-espresso.org
>> http://www.democritos.it/mailman/listinfo/wannier
> _______________________________________________
> Wannier mailing list
> Wannier at quantum-espresso.org
> http://www.democritos.it/mailman/listinfo/wannier


From joseph99077 at yahoo.com.tw  Tue May 22 16:10:12 2007
From: joseph99077 at yahoo.com.tw (joseph99077 at yahoo.com.tw)
Date: Tue, 22 May 2007 22:10:12 +0800 (CST)
Subject: [Wannier] about Amn
Message-ID: <846698.46490.qm@web72301.mail.tp2.yahoo.com>

hello
       I got a question about the matrix Amn.  in the pwscf package, we can generate Mmn and Amn. there is a term in the source code pw2wannier90.f90 around line 1090 , amn = ZDOTC(npw,evc(1,ibnd),1,sgf(1,iw),1). Can you please explain more about what kind of role do evc and sgf play in this statement.  From the user guide, I would say it's the inner product of Bloch states and trail functions. so, is sgf the trail function? ( I hope this question is not beyond the scope of the website.).  
       I hope that you can tell me how to generate wannier functions from the wannier package which you provided.  
      have a good day.



       ????????????? - ???? Yahoo!???????
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From degironc at sissa.it  Wed May 23 11:10:34 2007
From: degironc at sissa.it (Stefano de Gironcoli)
Date: Wed, 23 May 2007 11:10:34 +0200 (CEST)
Subject: [Wannier] about Amn
In-Reply-To: <846698.46490.qm@web72301.mail.tp2.yahoo.com>
References: <846698.46490.qm@web72301.mail.tp2.yahoo.com>
Message-ID: <Pine.LNX.4.64.0705231104450.2226@shannon-02.sissa.it>

in PWscf evc is the array containing the eigenvectors (the complex k+G 
Fourier coefficients of them); it's a global array used all around the 
code.
sgf is a local array created in the tool that builds the Amn matrix that 
contains the S matrix (for US pseudopotential, the identity matrix for NCPP)
times the guiding functions (hence the name).

hope it helps.

   Stefano de Gironcoli


On Tue, 22 May 2007, joseph99077 at yahoo.com.tw wrote:

> hello
>       I got a question about the matrix Amn.  in the pwscf package, we can generate Mmn and Amn. there is a term in the source code pw2wannier90.f90 around line 1090 , amn = ZDOTC(npw,evc(1,ibnd),1,sgf(1,iw),1). Can you please explain more about what kind of role do evc and sgf play in this statement.  From the user guide, I would say it's the inner product of Bloch states and trail functions. so, is sgf the trail function? ( I hope this question is not beyond the scope of the website.).
>       I hope that you can tell me how to generate wannier functions from the wannier package which you provided.
>      have a good day.
>
>
>
>       ?????????b???A?O???b???w?? - ???W?]?w Yahoo!?_???w???????I

From brad.malone at gmail.com  Fri May 25 21:58:31 2007
From: brad.malone at gmail.com (Brad Malone)
Date: Fri, 25 May 2007 12:58:31 -0700
Subject: [Wannier] Too many projections defined error
Message-ID: <bf16929a0705251258w77a15b35oa780121ad8dab79c@mail.gmail.com>

Hi, I'm having an issue that I'm very confused about.  I'm running a
calculation on silicon with 12 atoms per unit cell.  There is a gap in my
system (pwSCF tells me that 7.3 is the highest occupied state and 8.4 is the
lowest unoccupied state).  I just care about the valence bands and so I set
my upper energy window to 7.8 eV and set num_wann=24 (num_bands=32).  My
frozen energy window is the same as my larger window and it covers all 24
valence bands.  However, when I run the wannier code to generate the .nnkp
file it tells me the following error:

 param_get_projection: too many projections defined



Any help in understanding why this is would be greatly appreciated!

Best,
Brad
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From mostofi at MIT.EDU  Fri May 25 22:22:28 2007
From: mostofi at MIT.EDU (Arash A Mostofi)
Date: Fri, 25 May 2007 16:22:28 -0400 (EDT)
Subject: [Wannier] Too many projections defined error
In-Reply-To: <bf16929a0705251258w77a15b35oa780121ad8dab79c@mail.gmail.com>
References: <bf16929a0705251258w77a15b35oa780121ad8dab79c@mail.gmail.com>
Message-ID: <Pine.GSO.4.64L.0705251612270.18260@mint-square.mit.edu>

Dear Brad

I think the problem is in the "projections" block of the input file, not 
the energy windows. As you say, a 12 atom unit cell of silicon will need 24 
maximally localised Wannier functions (MLWFs) to span the valence manifold 
and this is the number of projections you should define in the projections 
block.

What we've found is that the generation of MLWFs for the valence manifold 
is very robust to the initial guess, so even specifying randomly centred 
s-orbital projections is good enough. This can be done by setting

Begin Projections
random
End Projections

in the input file.

Cheers

Arash

-----------------------------------------
Dr Arash A Mostofi
Dept of Materials Science and Engineering
13-4084 MIT
77 Massachusetts Avenue
Cambridge MA 02139-4307 USA
Tel: 617.2536026
-----------------------------------------

On Fri, 25 May 2007, Brad Malone wrote:

> Hi, I'm having an issue that I'm very confused about.  I'm running a
> calculation on silicon with 12 atoms per unit cell.  There is a gap in my
> system (pwSCF tells me that 7.3 is the highest occupied state and 8.4 is the
> lowest unoccupied state).  I just care about the valence bands and so I set
> my upper energy window to 7.8 eV and set num_wann=24 (num_bands=32).  My
> frozen energy window is the same as my larger window and it covers all 24
> valence bands.  However, when I run the wannier code to generate the .nnkp
> file it tells me the following error:
>
> param_get_projection: too many projections defined
>
>
>
> Any help in understanding why this is would be greatly appreciated!
>
> Best,
> Brad
>


From brad.malone at gmail.com  Sat May 26 20:57:30 2007
From: brad.malone at gmail.com (Brad Malone)
Date: Sat, 26 May 2007 11:57:30 -0700
Subject: [Wannier] Re: Too many projections defined error
Message-ID: <bf16929a0705261157j17698edejac937baf6142ec88@mail.gmail.com>

Thanks for the response Arash.  Setting the projections to random (they were
set to sp3) did indeed fix that issue.  I ran the wannier code and generated
the .nnkp file.  However, in the nnkp file it lists my excluded bands as
being 25-32 (which I had specified in the .win input file; perhaps
unnecessary because my window excludes them anyway) but also it lists band
#8 as being excluded, and I did not want or specify that.  Is there a reason
for this?  I'm worried that it may be causing me an error when I run the
Wannier code again because I get an error of "param_read: mismatch in
silicon.eig".  Inspecting the silicon.eig file it looks like it should be
okay, unless the code thinks that there are 23 bands (having excluded band
8), as there are 24 bands (for my 64 points) listed in the silicon.eig file.

I'm also interested in the bottom of the conduction band.  Do you have a
feel for how robust this is to the initial guess for the projections?  And
is it possible for me to specify sp3 projections without having 48 wannier
bands?  I'd like to use fewer bands if possible because it seems that I'm
running into memory allocation issues that prevent me from starting with a
denser k-grid. Thanks again for the help.

Brad



> Message: 1
> Date: Fri, 25 May 2007 12:58:31 -0700
> From: "Brad Malone" <brad.malone at gmail.com>
> To: wannier at quantum-espresso.org
> Subject: [Wannier] Too many projections defined error
>
> ------=_Part_139432_23760487.1180123111998
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Content-Transfer-Encoding: 7bit
> Content-Disposition: inline
>
> Hi, I'm having an issue that I'm very confused about.  I'm running a
> calculation on silicon with 12 atoms per unit cell.  There is a gap in my
> system (pwSCF tells me that 7.3 is the highest occupied state and 8.4 is
> the
> lowest unoccupied state).  I just care about the valence bands and so I
> set
> my upper energy window to 7.8 eV and set num_wann=24 (num_bands=32).  My
> frozen energy window is the same as my larger window and it covers all 24
> valence bands.  However, when I run the wannier code to generate the .nnkp
> file it tells me the following error:
>
> param_get_projection: too many projections defined
>
>
>
> Any help in understanding why this is would be greatly appreciated!
>
> Best,
> Brad
>
> ------=_Part_139432_23760487.1180123111998
> Content-Type: text/html; charset=ISO-8859-1
> Content-Transfer-Encoding: 7bit
> Content-Disposition: inline
>
> Hi, I&#39;m having an issue that I&#39;m very confused about.&nbsp;
> I&#39;m running a calculation on silicon with 12 atoms per unit cell.&nbsp;
> There is a gap in my system (pwSCF tells me that 7.3 is the highest
> occupied state and 8.4
> is the lowest unoccupied state).&nbsp; I just care about the valence bands
> and so I set my upper energy window to 7.8 eV and set num_wann=24
> (num_bands=32).&nbsp; My frozen energy window is the same as my larger
> window and it covers all 24 valence bands.&nbsp; However, when I run the
> wannier code to generate the .nnkp file it tells me the following error:
> <br><br><blockquote style="border-left: 1px solid rgb(204, 204, 204);
> margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"
> class="gmail_quote">&nbsp;param_get_projection: too many projections
> defined</blockquote><div><br><br>Any help in understanding why this is would
> be greatly appreciated!
> <br><br>Best,<br>Brad<br></div><br><br>
>
> ------=_Part_139432_23760487.1180123111998--
>
> --__--__--
>
> Message: 2
> Date: Fri, 25 May 2007 16:22:28 -0400 (EDT)
> From: Arash A Mostofi <mostofi at MIT.EDU>
> To: Wannier List <wannier at quantum-espresso.org>
> Subject: Re: [Wannier] Too many projections defined error
>
> Dear Brad
>
> I think the problem is in the "projections" block of the input file, not
> the energy windows. As you say, a 12 atom unit cell of silicon will need
> 24
> maximally localised Wannier functions (MLWFs) to span the valence manifold
> and this is the number of projections you should define in the projections
> block.
>
> What we've found is that the generation of MLWFs for the valence manifold
> is very robust to the initial guess, so even specifying randomly centred
> s-orbital projections is good enough. This can be done by setting
>
> Begin Projections
> random
> End Projections
>
> in the input file.
>
> Cheers
>
> Arash
>
> -----------------------------------------
> Dr Arash A Mostofi
> Dept of Materials Science and Engineering
> 13-4084 MIT
> 77 Massachusetts Avenue
> Cambridge MA 02139-4307 USA
> Tel: 617.2536026
> -----------------------------------------
>
>
>
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From brad.malone at gmail.com  Sun May 27 02:34:57 2007
From: brad.malone at gmail.com (Brad Malone)
Date: Sat, 26 May 2007 17:34:57 -0700
Subject: [Wannier] Re: Too many projections defined error
Message-ID: <bf16929a0705261734r430f204hed7e75f4a8f46cdf@mail.gmail.com>

Aha, I see now that it simply first lists the number of excluded bands
before listing the specific numbers.  But I'm still wondering about why I'm
getting the error in the .eig file.  Thanks!
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From brad.malone at gmail.com  Sun May 27 21:04:27 2007
From: brad.malone at gmail.com (Brad Malone)
Date: Sun, 27 May 2007 12:04:27 -0700
Subject: [Wannier] Re: Too many projections defined error
Message-ID: <bf16929a0705271204k7d8c406aq33a10d55d569e43e@mail.gmail.com>

Omitting the 'exclude bands' portion in my input file apparently fixes my
issue with the .eig file.  I no longer get the error.  I don't know if what
I described before is the reason for that or not, but it works now.

Best,
Brad
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From lanhaiping at gmail.com  Tue May 29 11:08:57 2007
From: lanhaiping at gmail.com (lan haiping)
Date: Tue, 29 May 2007 17:08:57 +0800
Subject: [Wannier] about WFs' display
Message-ID: <c92002fa0705290208x7aa4d366vc3e73d1f1e370ca7@mail.gmail.com>

Dear All,

   I am trying to display WFs with XCRSDEN, while there are some problems i
cannot solve .
Attached is one of my results,  the wf displayed is not full.  Would you
please tell me how to obtain
a full WFs display ? Are there some tricks to generate WFs ?  For my
calculation , the wout file gave that  Im/Re==0,
So, i confirmed that  there is no problem related with wannierise procedure.
In addition , the interpolated bands are also
consistent with PW results.

By the way, is there any way to generate multi-WFs in a single xsf file ?

Regards,

H.P


-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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From mostofi at MIT.EDU  Tue May 29 17:26:06 2007
From: mostofi at MIT.EDU (Arash A Mostofi)
Date: Tue, 29 May 2007 11:26:06 -0400 (EDT)
Subject: [Wannier] about WFs' display
In-Reply-To: <c92002fa0705290208x7aa4d366vc3e73d1f1e370ca7@mail.gmail.com>
References: <c92002fa0705290208x7aa4d366vc3e73d1f1e370ca7@mail.gmail.com>
Message-ID: <Pine.GSO.4.64L.0705291123530.27273@home-on-the-dome.mit.edu>

Dear Ian

I don't think your attachment made it through to my inbox, but the 
problem you describe may be resolved by setting

wannier_plot_supercell = 3

in the Wannier90 input file.

Cheers

Arash

-----------------------------------------
Dr Arash A Mostofi
Dept of Materials Science and Engineering
13-4084 MIT
77 Massachusetts Avenue
Cambridge MA 02139-4307 USA
Tel: 617.2536026
-----------------------------------------

On Tue, 29 May 2007, lan haiping wrote:

> Dear All,
>
>  I am trying to display WFs with XCRSDEN, while there are some problems i
> cannot solve .
> Attached is one of my results,  the wf displayed is not full.  Would you
> please tell me how to obtain
> a full WFs display ? Are there some tricks to generate WFs ?  For my
> calculation , the wout file gave that  Im/Re==0,
> So, i confirmed that  there is no problem related with wannierise procedure.
> In addition , the interpolated bands are also
> consistent with PW results.
>
> By the way, is there any way to generate multi-WFs in a single xsf file ?
>
> Regards,
>
> H.P
>
>
> -- 
> Hai-Ping Lan
> Department of Electronics ,
> Peking University , Bejing, 100871
> lanhaiping at gmail.com, hplan at pku.edu.cn
>


From jry20 at cam.ac.uk  Tue May 29 20:13:28 2007
From: jry20 at cam.ac.uk (Jonathan Yates)
Date: Tue, 29 May 2007 19:13:28 +0100 (BST)
Subject: [Wannier] about WFs' display
In-Reply-To: <Pine.GSO.4.64L.0705291123530.27273@home-on-the-dome.mit.edu>
References: <c92002fa0705290208x7aa4d366vc3e73d1f1e370ca7@mail.gmail.com>
 <Pine.GSO.4.64L.0705291123530.27273@home-on-the-dome.mit.edu>
Message-ID: <Pine.LNX.4.63.0705291842060.28110@tcmpc12.phy.cam.ac.uk>

On Tue, 29 May 2007, Arash A Mostofi wrote:

> I don't think your attachment made it through to my inbox, but the problem 
> you describe may be resolved by setting
>
> wannier_plot_supercell = 3


This is something of a FAQ, so maybe I can expand on the reasons behind 
Arash's answer.

Defns :  WF=Wannier Function  :   BZ=Brillouin zone

A WF is not periodic in the unit cell. Therefore it is not generally 
sufficient to plot it in a single unit cell.
  wannier_plot_supercell controls the number of units cell in which we 
construct the WF. For a value of 3 this means the home unit cell, and the 
26 neighbouring unit cells. This is normally sufficient to give a good 
picture of a WF.
  Plotting can be an expensive operation. You may wish to plot only a 
subset of the WF. You can control which WF are plotted using the 
wannier_plot_list keyword.

  The plotting of WF could be much improved. The next version of wannier90 
(due over the summer) will have improvements in this area.


  Another, related technical issue is that when the WF are computed from a 
finite sampling of the BZ they will be periodic in a supercell of the unit 
cell. For example a WF computed from a 4x4x4 sampling of the BZ will 
'live' in 4x4x4 supercell of the unit cell.
   This is apparent in Example 1 of Wannier90. If you plot WF in GaAs from 
a 2x2x2 BZ sampling using wannier_plot_supercell = 3 you will see the 
periodic images of the WF.


>> By the way, is there any way to generate multi-WFs in a single xsf file ?

  No.
   It would be trivial to make this modification. However, I don't think it 
would be very useful. As I understand it Xcrysden is able to plot a single 
isosurface, which maybe a weighted sum of several scalar fields, but not 
multiple isosurfaces (ie several WF at once). So putting all the WF in a 
single file would make Xcrysden very slow to start (it parses the entire 
xsf file on startup) to no real advantage.


  Jonathan


-- 
Dr Jonathan Yates         |    Theory of Condensed Matter Group
Corpus Christi College    |    Cavendish Laboratory
Cambridge, CB2 1RH, UK    |    Cambridge, CB3 OHE, UK
email jry20 at cam.ac.uk     |    Tel +44 (0)1223 337461