Brief Lab Overview

This lab will give you some hands-on experience with electronic structure theory as applied to small molecules in the gas phase. We will run computations on PC's using a graphical front-end to the Q-Chem quantum chemistry program package [#!Q-Chem-1.2!#]. You will choose a small molecule and use the computer program to obtain the equilibrium geometry, harmonic vibrational frequency, dipole moment, thermodynamic properties, etc. Then, you will choose another small molecule and obtain a Walsh diagram by obtaining the orbital energies at different geometries. The Walsh diagram will allow you to make simple predictions about the geometries of the ground and excited electronic states of your molecule. One component of the lab will be the investigation of how your predictions change when you use different levels of theory.

This lab module assumes you have already studied quantum chemistry at the undergraduate level. It aims more for a ``working knowledge'' of quantum chemistry, rather than a detailed mathematical understanding of the underlying theories. However, it is probably not possible to gain this working knowledge without at least some type of understanding of the quantum mechanical foundations. The background handout will hopefully teach you the fundamentals, and the suggested reading can provide additional information and fill in any blanks.

The real point of this lab isn't to have you run calculations, but to have you start to learn how to learn calculations for the purpose of making real predictions. Although you will make some comparisons to experiment, the real goal is to get you to think about how you would interpret your results if you didn't have any experimental data available. This lab has been made shorter on purpose to allow you time to do the required reading and to write a good lab report.