Hello Kwant users,

I am very new to kwant and I am still learning to use the code. So my
apologizes for any trivial questions.

I working on the tutorial notebooks I found in the here (
https://kwant-project.org/mm16). In the tutorial 3.4.graphene_qshe.ipynb I
am trying to visualize the zigzag graphene lattice created using the
kwant.Builder and .shape() module using kwant.plot(*sys*). I am getting the
following error

zigzag_ribbon = kwant.Builder(kwant.TranslationalSymmetry([1, 0]))
#zigzag_ribbon[graphene.shape((lambda pos: abs(pos[1]) < 9 and pos[1]%2
==1), (0, 0))] = 0.2
#zigzag_ribbon[graphene.shape((lambda pos: abs(pos[1]) < 9 and pos[1]%2
==0), (0, 0))] = -0.2
zigzag_ribbon[graphene.shape((lambda pos: abs(pos[1]) < 9), (0, 0))] = 0
zigzag_ribbon[graphene.neighbors(1)] = 1
zigzag_ribbon.finalized()
kwant.plotter.plot(zigzag_ribbon)
#kwant.plotter.bands(zigzag_ribbon.finalized());

---------------------------------------------------------------------------KeyError
                                 Traceback (most recent call
last)<ipython-input-84-0b886d56dec5> in <module>      5
zigzag_ribbon[graphene.neighbors(1)] = 1      6
zigzag_ribbon.finalized()----> 7 kwant.plotter.plot(zigzag_ribbon)
 8 #kwant.plotter.bands(zigzag_ribbon.finalized());
~/anaconda3/lib/python3.6/site-packages/kwant/plotter.py in plot(sys,
num_lead_cells, unit, site_symbol, site_size, site_color,
site_edgecolor, site_lw, hop_color, hop_lw, lead_site_symbol,
lead_site_size, lead_color, lead_site_edgecolor, lead_site_lw,
lead_hop_lw, pos_transform, cmap, colorbar, file, show, dpi, fig_size,
ax)    962     963     site_size = make_proper_site_spec(site_size,
fancy_indexing)--> 964     site_color =
make_proper_site_spec(site_color, fancy_indexing)    965
site_edgecolor = make_proper_site_spec(site_edgecolor, fancy_indexing)
   966     site_lw = make_proper_site_spec(site_lw, fancy_indexing)
~/anaconda3/lib/python3.6/site-packages/kwant/plotter.py in
make_proper_site_spec(spec, fancy_indexing)    907     def
make_proper_site_spec(spec, fancy_indexing=False):    908         if
callable(spec):--> 909             spec = [spec(i[0]) for i in sites
if i[1] is None]    910         if (fancy_indexing and
_p.isarray(spec)    911             and not isinstance(spec,
np.ndarray)):
~/anaconda3/lib/python3.6/site-packages/kwant/plotter.py in
<listcomp>(.0)    907     def make_proper_site_spec(spec,
fancy_indexing=False):    908         if callable(spec):--> 909
     spec = [spec(i[0]) for i in sites if i[1] is None]    910
if (fancy_indexing and _p.isarray(spec)    911             and not
isinstance(spec, np.ndarray)):
~/anaconda3/lib/python3.6/site-packages/kwant/plotter.py in
site_color(site)    956             color_mapping = dict(zip(families,
cycle))    957             def site_color(site):--> 958
 return color_mapping[site.family]    959         else:    960
    # Unknown finalized system, no sites access.
KeyError: kwant.lattice.Monatomic([[1.0, 0.0], [0.5,
0.8660254037844386]], [0.0, 0.5773502691896258], '1', None)


However, I am able to plot the dispersion and all that. Also, I am able to
visualize the square lattice presented in other tutorials. Do we have to do
something different to visualize non-square lattice ?

Thanks for your help
-- 
Srilok Srinivasan
Graduate Student
Mechanical Engineering
Iowa State University, Ames, IA

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