Example 1: Water

Z-Matrices

Students

This is the water molecule.

This is the numbered molecule. Use this for reference in this example.

1. Label the oxygen as atom O1. Since the O1 atom is placed at the origin, you don't need to define it. Thus far, your z-matrix looks like this:
   O1

2. Either hydrogen can be labelled as H2 and the other as H3.
3. Starting with the H2 atom, we use the reference charts and find that the bond length between a single bond hydrogen-oxygen is 0.96 angstroms. Now your z-matrix should look like this:

   O1
   H2	1	0.96

4. Finally, we want to describe atom H3. To do this, we first look at its bond length with atom O1. Again, using the reference charts, we find the bond length = 0.96 angstroms. We must also find the bond angle formed by the three atoms. Using the reference charts, we find this angle to equal 110.0 degrees. Your final z-matrix should look like this: