[Wannier] spread

[Nicola Marzari]

Dear Vivek,


first of all, is your unit cell a long strip ? I'm a bit surprised
by the fact that you only sample 1 k-point in 2 out of 3 directions.

Also, have you tried a simple BN-sheet unit cell with only two atoms ?
My guess it that the WFs should look like bonds between the atoms in
the plane, and then on each N you have a p_z like orbital.

Not sure on the multiplication of points in the nscf - that usually
shouldn't happen, exactly because nscf should just do the points it's
told.

			nicola


Vivek Ranjan wrote:
> Hello,
> 
> I am trying to calculate wannier function of BN sheet. The way the unit
> cell is constructed, I have chosen (12,1,1) kpoint mesh for scf
> calculation. Then I do an nscf calculation with 4 kpoints (4,1,1). The
> spread of one of wannier function is 26 A. I run several steps (more than
> 20000) and still it does not converge. The question is how to reduce this
> spread ?
> 
> I tried putting more kpoints by doing (12,2,2) scf calculations and 16
> kpoints (4,2,2) for nscf and wannier parts. The problem is instead of 16
> kpoints in the nscf that I hand put in the file, pwscf always generates 24
> kpoints. The additional kpoints are shifted kpoints that I put. It never
> happened to me before and wondering why it is happening ?
> 
> (12,1,1) scf, and (4,1,1) kpoints has no such problems.
> 
> Thanks,
> 
> Vivek,
> Physics, NCSU.
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Prof Nicola Marzari   Department of Materials Science and Engineering
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