Key Points for Basis Sets:

Basis Sets Lab Activity

Students

• Molecular orbitals allow scientists to mathematically express the properties of molecules.
• In order to run computational chemistry programs, the scientist must enter three things:
  1. A starting molecular geometry
  2. The properties to be calculated
  3. A starting set of mathematics called the basis set function
• There are two main types of basis set functions:
  1. Minimal Basis Sets
  2. Extended Basis Sets
• Basis sets are calculated using two types of equations:
  1. Slater Type Orbitals (STOs)
     
  2. Gaussian Type Orbitals (GTOs)
     
• STOs are more exact, but take much longer to calculate than GTOs.
• By adding several GTOs you get a good approximation of the STO.
• Basis sets are named in the form: STO-NG
  This means that you are modeling a STO calculation, with "N" number of GTOs. Asterisks at the end would imply an extended basis set.