Oops, never mind my remark about the documentation being incorrect! It was just because discretize_symbolic returns a tuple which you fed as a first argument to build_discretized. On Fri, Mar 29, 2019 at 3:28 PM Bas Nijholt wrote:

It seems like the documentation here https://gitlab.kwant-project.org/kwant/kwant/blob/fdd4674/kwant/continuum/di... is wrong because it expects a dictionary.

I see that you do

template = kwant.continuum.discretize_symbolic(hamiltonian) t = kwant.continuum.build_discretized(template, coords = ('x','y','z'))

However, discretize_symbolic returns two variables. Instead do:

template, coods = kwant.continuum.discretize_symbolic(hamiltonian) t = kwant.continuum.build_discretized(template, coords)

The list of coods should be passed to discretize_symbolic. However, if you omit it, it will be inferred from your Hamiltonian’s k_{x, y, z} terms.

Best, Bas

On Fri, Mar 29, 2019 at 3:11 PM Naveen Yadav wrote:

...

Hi Bas,

Thanks for your reply.

I have used the same syntax. But it is showing an Attribute Error: 'tuple object has no attribute 'items'

from __future__ import division import kwant import kwant.continuum import scipy.sparse.linalg import scipy.linalg import numpy as np import sympy from math import sin, cos, sqrt, pi import matplotlib.pyplot as plt hamiltonian = ("""k_x**2 + k_y**2 + k_z**2""") hamiltonian = kwant.continuum.sympify(hamiltonian) template = kwant.continuum.discretize_symbolic(hamiltonian) t = kwant.continuum.build_discretized(template, coords = ('x', 'y', 'z')) print(t)

AttributeError Traceback (most recent call last)<ipython-input-12-9780451ce368> in <module> 11 hamiltonian = kwant.continuum.sympify(hamiltonian) 12 template = kwant.continuum.discretize_symbolic(hamiltonian)---> 13 t = kwant.continuum.build_discretized(template, coords = ('x','y','z')) 14 print(t) 15 hamiltonian /usr/local/lib/python3.6/dist-packages/kwant/continuum/discretizer.py in build_discretized(tb_hamiltonian, coords, grid_spacing, locals) 281 282 with reraise_warnings():--> 283 for k, v in tb_hamiltonian.items(): 284 tb_hamiltonian[k] = sympify(v, locals) 285 AttributeError: 'tuple' object has no attribute 'items'

What should I do.

Naveen

On Fri, Mar 29, 2019 at 5:37 PM Bas Nijholt wrote:

...

Hi Naveen,

In the documentation https://kwant-project.org/doc/dev/reference/generated/kwant.continuum.build_... you can see that coords require a sequence of strings, so for example:

coords = ('x',) # for 1D coords = ('x', 'y', 'z') # for 3D

Best, Bas

On Fri, Mar 29, 2019 at 12:59 PM Naveen Yadav wrote:

...

I want to know more about the builid_discretized(tb_hamiltonian, coords). I did not undersand what should be the syntax to write the coords.Could you please help me by sending an example code for writing coords?

Thanks in Advance.

Naveen Department of Physics & Astrophysics University of Delhi 110007

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With Best Regards NAVEEN YADAV Ph.D Research Scholar Deptt. Of Physics & Astrophysics University Of Delhi.