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.

open paraview

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.

open paraview

Fig. 7.4.1 open paraview

What should appear is a color plot of the potential applied to the system.


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.

open paraview

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.

open gs

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.

clip tool

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.

clipped gs

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.

clipped gs z

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.


Fig. 7.5.5 left_right

We will then see an empty ParaView window on the right.

empty right

Fig. 7.5.6 empty right

From there, we can open the first excited state in this second view window.


Fig. 7.5.7 excited_state

From here, we can also take linecuts using the plot over line tool.


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.

Line plot

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.