Tutorial:Particle in an octopus

From OctopusWiki
Jump to: navigation, search

Octopus can actually run 2D systems where the shape of the simulation box is defined by what is white in an image file. Here is an example of a "particle in an octopus", in which we have a constant potential and an octopus-shaped quantum dot. To run it, you will need to have built the code with the optional library GDLIB.


For this example we will need two files:


CalculationMode = gs
FromScratch = yes
Dimensions = 2

"null" | species_user_defined | potential_formula | "0" | valence | 1

"null" | 0 | 0

BoxShape = box_image
BoxShapeImage = "gdlib.png"

ff = 20
 135 / ff | 95 / ff

TheoryLevel = independent_particles
ConvEigenError = yes


Make this file available in the run directory. You can download it by clicking on the image bellow. It is also available in the PREFIX/share/octopus directory from your Octopus installation.



You can obtain the wavefunction by adding this to the input file:

Output = wfs
OutputFormat = plane_z

and rerunning. View it in gnuplot with

plot 'static/wf-st0001.z=0' u 1:2:3 linetype palette


splot 'static/wf-st0001.z=0' u 1:2:(0):($3*500) with pm3d

Where does the wavefunction localize, and why?


  • See how the total energy scales with the size of the system (controlled by the ff parameter in the input file). How does it compare to the formula for a particle in a box?
  • Look at the wavefunctions of the unoccupied states.
  • Think of a serious application that would use the ability to define the simulation box by an image!

Previous 1D Helium -

Back to Model systems