Simple Huckel Molecular Orbitals (SHMO)

SHMO theory finds the electronic energy levels of a molecule and its corresponding molecular orbitals (MO). Only organic, planar (2 dimensional) molecules with delocalized electrons work well with this theory. The most commonly known delocalized carbon structure is that of benzene, a six membered ring in which six p-atomic orbitals (AO) of the carbon atoms combine in phase and out of phase to form a set of six π-MOs.

Instructions

• Use the Add button to add atoms to the canvas and drag the mouse from one atom to another to create bonds.

• Use the Minimize button to relax the molecule to resemble its normal structure. The process uses Newton's equation to find common angles for ring structures and adjusts chains to 120 degrees.

• Use the Show Orbitals button or click on an energy level to view the MO's (open blue for +ve phase, above plane and solid red for -ve phase, below plane) for that particular energy level and the energy defined as a function of the coulomb integral α and resonance integral β, i.e α±xβ (top left)

• Use the Show Data Table button to show the eigen values for all energy states and the coefficients that define the contribution of each AO in the eigen vector defining each MO. Also calculated are the realtive charge densities on each atom and bond orders.

• Note: Check the On-the-fly Calc box to automatically add energy levels and electrons to the Energy Graph to the right of the canvas. Check the Verbose box to include the coefficients of the AOs that make up the MO for the particular energy state selected.

• Use the Change button and select an atom to alter its properties, e.g add hetero-atoms. Use Erase to delete individual atoms or Clear to start over. Use Move to re-position and Rotate to re-orientate the molecule. Change the net charge on the molecule with + and - buttons (bottom left). 

GNU General Public License