Calculation of three-body contribution to the stabilization energy (the three-body energy) in a trimer. Basis set superposition error correction scheme where all subsystems are calculted in the trimer basis is applied by default but can be switched off. The setup for the monomers within the trimer is analogous to interaction energy calculations.
In a trimer ABC, it is defined as:
What is, for practical calculations, it can be recasted in terms of energies as: