Example of a Simple Page Showing the Results of an ab initio Computation of Ethane Structure
This geometry optimization was done using a 3-21G basis set for a restricted Hartree-Fock computation using the package GAMESS.1,2

Note on how this page was made: This page was generated using the "Pop-in" template of the "Export to Web..." function of Jmol.  The arrangement of the Jmol applets on this page is not the default.  The applets were moved around in a WYSIWYG editor by cutting and pasting the "div's" containing the javascript and static image for each applet.  These "div's" have class ID="JmolDiv". 
 
Geometry of ethane optimized at the 3-21G level using restricted Hartree-Fock. Experimental geometry of ethane from the NIST Computational Chemistry Comparison and Benchmark Database.
The geometry optimization at the 3-21G level of theory yields very good results.  This can be seen by comparison of the computational results with the experimental geometry at right.   The image can be converted to a live 3-D model by clicking on the link in the image.

The 3-21G basis set is a pretty small basis set by modern standards, but is clearly adequate for determination of geometries of simple hydrocarbons.


 
Representation of 1rst HOMO of ethane as determined using a 3-21G RHF calculation. Representation of 2nd HOMO of ethane as determined using a 3-21G RHF calculation
The images at left show the two degenerate highest occupied molecular orbitals (HOMO) in ethane. Note that these orbitals are anti-bonding in character along the C-C bond, but bonding in character along the C-H bonds.  Also notice that there is some bonding interation between hydrogens on the same carbon atoms in the leftmost orbital(blue lobe).
 
Representation of the LUMO of ethane as determined using a 3-21G RHF calculation.
This image represents the electron density distribution if an electron were to enter the lowest unoccupied molecular orbital (LUMO) of ethane.  Notice that this suggests that electron rich species will interact most strongly with ethane either end-on or with one of the hydrogens.
  1.  "General Atomic and Molecular Electronic Structure System" M.W.Schmidt, K.K.Baldridge, J.A.Boatz, S.T.Elbert, M.S.Gordon, J.H.Jensen, S.Koseki, N.Matsunaga, K.A.Nguyen, S.Su, T.L.Windus, M.Dupuis, J.A.Montgomery J. Comput. Chem., 14, 1347-1363(1993).
  2.  "Advances in electronic structure theory: GAMESS a decade later" M.S.Gordon, M.W.Schmidt pp. 1167-1189, in "Theory and Applications of Computational Chemistry: the first forty years" C.E.Dykstra, G.Frenking, K.S.Kim, G.E.Scuseria (editors), Elsevier, Amsterdam, 2005.
By J. Gutow, 2008
Based on template by A. HerrŠez as modified by J. Gutow
Page skeleton and JavaScript generated by export to web function using Jmol 11.6.6 2008-09-20 22:06 on Nov 23, 2008.