7. Visualizing QTCAD quantities with ParaView
7.1. Requirements
7.1.1. Software components
ParaView
7.1.2. References
7.2. Briefing
The goal of this tutorial is to demonstrate how to visualize certain
quantities generated by QTCAD using ParaView. The quantities we
will be visualizing are those simulated in
creating_dot.py
(see Schrödinger equation for a quantum dot for details).
7.3. Opening ParaView
The first step to visualizing the QTCAD quantities is to open ParaView. Clicking on the icon should lead you to the following GUI.
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Fig. 7.3.1 open paraview
We close the popup and are ready to begin.
7.4. Visualizing the potential
We start by looking at the conduction band edge. We use the
file>open
menu to select the file containing the conduction band
edge in .vtu
format.
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Fig. 7.4.1 open paraview
What should appear is a color plot of the potential applied to the system.
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Fig. 7.4.2 cd_V
We see that along the \(x\) direction, the potential has 2 barriers in dark red. We should also be able to make out the parabolic nature of the potential along the \(y\) and \(z\) directions.
Before moving on to visualizing the wavefunctions, we will delete the conduction band edge plot using the delete button on the left.
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Fig. 7.4.3 open paraview
7.5. Visualizing wavefunctions
Next we visualize the wavefunctions. We start by opening the .vtu
file containing the ground state.
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Fig. 7.5.1 open gs
What we see when the file opens is the value of the wavefunction on the
outer boundary of the dotmesh
. To see the wavefunction inside this
region, we use the clip tool which is the third tool on the menu bar.
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Fig. 7.5.2 clip tool
Once selected, we can choose where the structure will be clipped by
modifying the origin
in the plane parameters
on the right-hand
side.
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Fig. 7.5.3 clipped gs
We can also use the plane parameters to define the normal vector of the clip, e.g. along the \(z\) direction in this example.

Fig. 7.5.4 clipped gs z
From these clips, we can see that the electron is concentrated at the center of this structure.
Then, in the top right corner, we can choose to split the screen from left to right.
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Fig. 7.5.5 left_right
We will then see an empty ParaView window on the right.
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Fig. 7.5.6 empty right
From there, we can open the first excited state in this second view window.
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Fig. 7.5.7 excited_state
From here, we can also take linecuts using the plot over line
tool.
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Fig. 7.5.8 plot_over_line
The two points used to define the line can be specified on the right
under the line parameters
heading. The line can also be seen in the
view window.
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Fig. 7.5.9 Line plot
The resulting line plot along x shows the sinusoidal wavefunction we expect for a particle-in-a box potential.
7.6. Conclusion
Presented above are the main tools we use in ParaView to analyze outputs of QTCAD. However, ParaView is very flexible. There are therefore most likely other tools that may also be useful.