[Wannier] Initial choice for projection

[seunghwan lee]

Dear Young-Su and Nick,

I looked at the initial orbitals I set in the .win file and they are 
actually consistent with what you suggested. I tried 2 unit cell as well
and got the same error message. (I attached .win file and scf input file 
for 2 unit cell)

   In dis_proj_froz... done
     1    95    95  1.001183578513  0.000000000000
 The trial orbitals for disentanglement are not orthonormal
 Exiting.......
 Error in dis_main: orthonormal error 1

It looks like the problem is in NORMALIZATION of orbital #95 (s-orbital, 
if W90 keep the ordering of initial orbitals), not orthogonality.
But it is difficult to understand that same orbitals defined in W90 are 
normalized at one location and not normalized at another location.

There is a couple of even more strange behavior.

[1] If I change the number of significant figures for the location of
initial orbital, the nomalization changes. For example, if I use

c= 3.3780, -0.7128, -0.6157 :pz :z = 3.3780, -0.7128, 0.0000 :x=0,0,1

the error message was

--------------------------------------------------------------
 1    95    95  1.006000381851  0.000000000000
 The trial orbitals for disentanglement are not orthonormal
 Exiting.......
-------------------------------------------------------------

But, if I use

c= 3.378034, -0.712837, -0.615700 :pz :z = 3.378034, -0.712837, 0.000000 :x=0,0,1

the error message was

--------------------------------------------------------------
     1    95    95  1.001183578513  0.000000000000
 The trial orbitals for disentanglement are not orthonormal
 Exiting.......
-------------------------------------------------------------

Why normalization is anything to do with the location of orbitals?

[2] If I change the order of initial orbitals in the input file,
I am still getting the error for orbital #95. So, it is not really
a problem of orbital #95 in the previous input file.

It is possible that I made some stupid error in the input file 
(see my attached input), but it looks like there is something strange 
going on with normalization for a large carbon nanotube. But, PRL paper
(Lee, Nardelli and Marzari) used even larger nanotube and, so it has to 
work. Any idea what might cause this kind of behavior? I am wondering
if you used different initial projections for 5 unit cell calculations 
reported in PRL paper.

Thank you. I really appreciate your help.

Seunghwan Lee




--- On Thu, 10/29/09, Young-Su Lee <lee0su at kist.re.kr> wrote:

> From: Young-Su Lee <lee0su at kist.re.kr>
> Subject: RE: [Wannier] Initial choice for projection
> To: "'seunghwan lee'" <seung43210 at yahoo.com>
> Cc: Wannier at quantum-espresso.org
> Date: Thursday, October 29, 2009, 9:20 PM
> 
> >I thought "random" means pz orbital on each carbon and
> s orbitals on random 
> >places (according to the user manual). But, still, it
> can't be a good
> >choice as you said. Where should I look to get
> H-matrix?
> 
> Yes, you are right. I got confused.
> To get H-matrix, turn on hr_plot option:
> 
> hr_plot = .true.
> 
> then you'll have seedname_hr.dat
> If you run transport part, then the code outputs "Maximum
> imaginary part of the real-space Hamiltonian".
> 
> >In nanotube case, I have at least an example to
> compare. But, if I have a
> >system that has never been investigated, how do I know
> that the results of
> >W90 calculation are correct if the results depend so
> much on the initial choice of projection?
> 
> But, if you start from reasonably good initial guesses,
> they'll give you the same WFs after dis+loc in most (not
> all) cases.
>   
> You may check things like these
>  1) Do WFs match well with our chemical intuition of
> (anti-)bonding?
>  2) Are all the elements of H matix real?
>  3) Do the interpolated band structure look okay?
> 
> Young-Su
> 
> 
>

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