[Wannier] Initial choice for projection

[seunghwan lee]

Dear Nick,

Thank you for your reply to my questions. I attached cnt55.win file 
(80 carbon) for your review. In this .win file, I tried to duplicate the 
initial projections given in the example.

I guess the problem is the orientaion of initial orbitals. The center of 
my 4 unit cell nanotube is not (0,0,0), whereas the center of 1 unit cell
(example) is (0,0,0). I'll try to fix this problem. Please let me know if
you see something different in my .win file.

Regards,

Seunghwan Lee
University of North Carolina

--- On Wed, 10/28/09, Nicholas E. Singh-Miller <nedward at MIT.EDU> wrote:

> From: Nicholas E. Singh-Miller <nedward at MIT.EDU>
> Subject: Re: [Wannier] Initial choice for projection
> To: "seunghwan lee" <seung43210 at yahoo.com>
> Cc: Wannier at quantum-espresso.org
> Date: Wednesday, October 28, 2009, 8:39 PM
> Dear Seunghwan,
> 
> The case of the CNT is a bit trickier (that other cases) to
> wannierize to the correct final configuration.
> 
> > 
> > Begin Projections
> > Random
> > C:pz:x=0,0,1
> > End Projections
> > 
> > It went through without a problem although the final
> results (band
> > structure, DOS) were somewhat different from the
> example.
> 
> Because the example case is well tested and carefully set
> up, this
> is a good indication that the final Wannier functions are
> probably not what you want.
> 
> > 
> > The trial orbitals for disentanglement are not
> orthonormal
> > Exiting.......
> > Error in dis_main: orthonormal error 1
> > 
> > I even tried the same projection like the one in
> example for 4 unit cells,
> > but it didn't work neither with the same error
> message.
> 
> You may want to include your .win file so others can see
> the exact set up.
> 
> > [3] What is the best option for initial projection in
> carbon nanotube
> > system?
> 
> It seems the best option for CNTs is the way they are set
> up in the example.  That is place "s" states on the
> bond centers and "p_z" states on each carbon.  The key
> is to have the p_z point out of the CNT. for instance (from
> the example):
> c=   3.3780, -0.7128, -0.6157 :pz :z= 
> 3.3780, -0.7128,  0.0000 :x=0,0,1
> 
> this is saying that a center (in cartesian coords) 3.3780,
> -0.7128, -0.6157 should have a pz projection.  the z=
> and x= are the axis for this orital (which will lie along
> z).  so for this case, because the CNT is
> longitudinally along the z-axis, we have to reset the
> x=0,0,1 and the z is pointing out from the center of the CNT
> (which you could acomplish by using the orientation
> (x-x0,y-y0,0) where x0,y0 is the center of the CNT, in this
> case that is 0,0 so the coords are the same as the wannier
> center).
> 
> Where as in your previous test C:pz:x=0,0,1
> the z-axis is not redefined (and would be the default
> z=0,0,1 ... which may be the cause of your orthonormality
> problems).
> 
> In general, I think that the CNT is a tricker problem than
> some of the others (e.g. there are times for other systems
> where choosing a random starting projection could work).
> 
> regards,
> 
> Nick
> 
> 
> *****************************************
> Nicholas E. Singh-Miller
> Prof. Marzari Group (quasiamore.mit.edu)
> Materials Science and Engineering
> Massachusetts Institute of Technology
> 13-4066
> (617)324-0372
> *****************************************
>


      
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