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 

2015-08-05 6:08 GMT-03:00 Maximilian Trescher <>:
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

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

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

(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 this
problem in Lapack?

I would be thankful for any hint,

César Núñez Ramírez
Doctor(C) Física