[Wannier] Kmesh errors

[Jonathan Yates]

On Sat, 1 Sep 2007, Brad Malone wrote:

> Hi, I am trying to generate the .nnkp file for a system that I am studying
> with a 6x6x3 grid and I am getting an error saying that the completeness
> relation from MV appendix B is not being satisfied.  So I looked at that
> paper and saw them mention that I could include more shells, so I added more
> shells (the code selects only shells 1 and 2 automatically).  However, when
> I do this either I get the same error or I get another error saying that
> "kmesh_shell_fixed: Singular Value Decomposition has found a very small
> singular value" (depending on which shells I select).  Is there something
> else that I can do to get around this?  I'm not sure what else I can modify.

Brad,

  wannier90 tries to pick a set of k-point shells that satisfies the B1 
condition. The scheme for doing this is described in our recent cond-mat 
(arXiv:0708.0650v1)

The automatic routine is pretty robust. Two things that can upset it
1) Not giving kpoints in the win file to enough dp (use the kmesh.pl 
script, it should pick the correct accuracy)
2) Not giving the unit cell to enough dp (eg for hexagonal cells)

  If you eliminate both of these then send me your win file - I'd like to 
find out why the automatic routine is getting stuck.

  Thanks
   Jonathan

ps. I remember I haven't answered your earlier question yet...

-- 
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