CHM
6V39
Basis Set Exercises
Due
Feb. 17, 2005
You are to calculate the Hartree-Fock equilibrium geometry, the total
energy, the orbitals, and the ionization potential for both HCl and
ethylene using a variety of basis sets. Tabulate the H-Cl distance, the
total energy, and the ionization potential (= -E for the highest
occupied MO [HOMO] by Koopman’s theorem) for HCl. Make a similar table
for ethylene, where there are more relevant geometries: the H-C-H
angle, the H-C-C angle, the C-H distance, and the C=C distance. Obtain
the experimental geometries and ionization potentials from the
literature, and report them too for comparison.
Basis sets to use are:
STO-3G
3-21G*
6-31G*
6-31G**
6-31+G**
Review your orbitals in each case and show that the number of basis
functions is as expected, given the description of the basis set in
Hehre. Describe the HOMO in each case. Note that for HCl there are two
degenerate (energetically identical) HOMOs.