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I have written up a previous answer which addresses how to predict an interaction energy ($E_{\mathrm{int}}$) which is completely different from a binding energy ($E_{\mathrm{bind}}$). However, much of the concepts will remain the same. I will try to outline here what in fact is the difference between an interaction energy and a binding energy. Unfortunately, 'binding energy' is tossed around a lot in the literature and consequently grossly misused. I hope to clarify the subtle differences between these two terms in my answer to your question.

I have written up a previous answer which addresses how to predict an interaction energy ($E_{\mathrm{int}}$) which is completely different from a binding energy ($E_{\mathrm{bind}}$). However, much of the concepts will remain the same. I will try to outline here what in fact is the difference between an interaction energy and a binding energy. Unfortunately, 'binding energy' is tossed around a lot in the literature and consequently grossly misused. I hope to clarify the subtle differences between these two terms in my answer to your question.

$E_{int} = E_{opt-dimer} - (E_{mon1} + E_{mon2})$

$E_{bind} = E_{opt-dimer} - (E_{opt-mon1} + E_{opt-mon2})$

As far as tools go, you can choose from a number of available quantum software packages. Gaussian 09 is a popular choice but very expensive. Q-Chem (paid) has the benefit of having the most beautiful, gorgeous, well-laid out documentation of anything I've ever seen (makes for a good supplemental textbook to boot). NWChem is free I think. Google can help you find plenty of options.

$E_{\text{int}} = E_{\text{opt-dimer}} - (E_{\text{mon1}} + E_{\text{mon2}})$

$E_{\text{bind}} = E_{\text{opt-dimer}} - (E_{\text{opt-mon1}} + E_{\text{opt-mon2}})$

As far as tools go, you can choose from a number of available quantum software packages. Gaussian 09 is a popular choice but very expensive. Q-Chem (paid) has the benefit of having the most beautiful, gorgeous, well-laid out documentation of anything I've ever seen (makes for a good supplemental textbook to boot). NWChem is opensource. Google can help you find plenty of options.

One last important note: When determining differences of energies (such as you do to get an interaction or binding energy), ALL energies being compared must be evaluated at the SAME LEVEL OF THEORY (method/basis set, etc.).