Dear All

I have the same problem when used the Kane-Mele model. The problem disappears when the next-nearest-neighbor hopping is zero or lower than 0.0005j. Some ideas for fix it?

Best Regards

César

2015-08-05 6:08 GMT-03:00 Maximilian Trescher <maximilian.trescher@fu-berlin.de>:

Dear kwant users and developers,

this is my first post to this list, I'm a PhD student from Berlin.

Currently I'm trying to implement a lattice model of a pyrochlore slab

in kwant.

I found a (more or less straightforward) way to introduce periodic

boundary conditions in the system in the maillinglist archive.

This works very nicely as long as I keep the periodicity along a lattice

vector.

But I run into problems when I choose different directions: Most of the

time all solvers fail with a

"LinAlgError: QZ iteration failed to converge in zgges".

I know about this post

http://comments.gmane.org/gmane.comp.science.kwant.user/372

but in my case it occurs not only for a band bottom, but for a range of

energies.

To give you all the details I prepared a Ipython notebook that you can

view here:

http://nbviewer.ipython.org/gist/faucon/729050da5e3f2eae1bb8#

(Note that the inclusion of complex next-nearest-neighbor hopping is

crucial to produce the error, I tried to create the shortest example

which reproduces my problem).

Do you have any idea how to circumvent this problem?

Is it somehow related to

http://netlib.org/lapack/Errata/vrac/lapack_known_issues.html#QZ this

problem in Lapack?

I would be thankful for any hint,

Best,

Maximilian

César Núñez Ramírez

Doctor(C) Física

U.T.F.S.M.