How to calculate binding energy using Gaussian 09?

In gaussian16, they have automate the binding energy calculations, you just need to run single point calculation with counterpoise correction via defining the atom-pairs.

Note: Above step need to be done on the optimized complex.

or

- Optimize the molecule AB with the the keyword opt+frequency for the minimum energy

- Find out the minimum energy A and B separately using the same keyword as above.

- Now subtract the energy as

Binding energy of AB =AB - (A+B)