Why calculate wavefunctions?
· To understand and predict the structure and reactions of molecules, we need to know about how electrons are arranged in them.
·
To study electrons, we need to use quantum mechanics.
·
In principle, all the information we need about a molecule is
contained in its wavefunction (the wavefunction is a function of the
coordinates of all the electrons and all the nuclei).
·
The trouble is, these are difficult to calculate.
·
We can make a first simplification by concentrating on the
wavefunction for the electrons separately from that of the nuclei (the
Born-Oppenheimer approximation).
·
The electronic wavefunction for a molecule will tell us all
about its electronic structure - i.e. how the electrons are arranged in the
molecule.
But how do we
find the electronic wavefunction?