[Wannier] Initial choice for projection
Nicholas E. Singh-Miller
nedward at MIT.EDU
Thu Oct 29 01:39:29 CET 2009
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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