The Simple Huckel Molecular Orbital Theory Calculator

[Introduction]   [FAQ]  

If you can read this you better read "My web browser doesn't support Java 1.1. What can I do?" in the FAQ below.

Introduction to SHMO

SHMO is an interactive program to perform electronic structure calculations within the "Simple Huckel Molecular Orbital" approximations. The theoretical basis for the method is described in Orbital Interaction Theory of Organic Chemistry, by A. Rauk (Wiley Interscience, 1994), Chapters 3 and 5. SHMO is designed as a teaching aid and replaces the earlier version distributed with the book. Besides performing conventional SHMO calculations, SHMO permits easy changes of orbital electronegativities (the Huckel coulomb integrals, alpha) and intrinsic orbital interaction values (the Huckel resonance integrals, beta) to illustrate the effects of interacting orbital energies orbital energy differences and overlaps on the resultant molecular orbital energies and polarizations. The program has been written entirely in the Java language by Richard Cannings.

The format and display of SHMO are compatible with usage in Orbital Interaction Theory of Organic Chemistry. Orbitals are displayed as filled and open coloured circles. Orbital energies are displayed relative to alpha in units of |beta|. Orbital selection is by clicking on the orbital energy display or step up/step down buttons. Heteroatoms, X, are incorporated as aX = alpha + hX|beta|, and bXY = kXY|beta|, where the default values of the parameters, hX and kXY, are taken from the literature. Thus for C, hC = 0.0 and kCC = -1.0. Atoms and bonds may be Added, Erased, or their types Changed at any time by simple mouse clicks. The number of electrons may be adjusted at any time and the net charges and bond orders displayed. All aspects of the calculation are printable.

    How do I use SHMO?
    What does this applet do? (for non-chemists) (includes a crash course on how to use SHMO)
    How can a get a copy?
    Who do I send bug reports to?
    My web browser doesn't support Java 1.1. What can I do?

This website is managed by:
Arvi Rauk , and,
Rich Cannings ,
Updated: August 25, 2000