Orbis is a piece of Python software I wrote for performing Simple Huckel Molecular Orbital analysis calculations. Orbis is designed to be an easy to use method for estimating a variety of molecular orbital properties including:

  • molecular orbital energies (SHMO eigenvalues and eigenvectors)
  • pi bond orders
  • net charges per atom
  • atom-atom polarizabilities
  • atom-bond polarizabilities

Orbis comes pre-loaded with a number of different atom and bond types but also allows for custom atom and bond types to be created. A simple sketchpad allows you to draw molecules and watch the eigenvalues, eigenvectors, energy level diagrams, molecular orbitals and more be calculated on the fly.

Orbis also has a number of other useful features including:

  • Interactive Energy Level Diagrams : Click an energy level to see the corresponding molecular orbital and eigen vectors
  • Handles larges complex molecules with different atom types
  • Save your sessions to update later
  • Export your results to a spreadsheet format
  • Import a Huckel matrix from a text file and Orbis will automatically draw your molecule!
  • Import molecules from Molfiles (.mol) and XYZ (.xyz) chemical file formats.
  • General matrix solver mode for solving problems other than pure pi-electron systems.


Download either a Windows installer for the original version of Orbis or check out an upcomping (incomplete) open source version on github.

Orbis in action...

Check out some of the screenshots of Orbis in action or watch this short video showing how you would create a simple benzene ring and then convert it to pyridine by changing one of the atom types.
Watch in HD full screen for best effect

Or this video of Orbis displaying the 24 membered molecule Coronene