Three-Body Energy Decomposition Analysis Based on the Fragment Molecular Orbital Method.

An energy decomposition analysis is developed for the three-body expansion of the fragment molecular orbital method at the level of density functional theory, density-functional tight-binding, coupled cluster, and other quantum-mechanical approaches in vacuum and solution. It is shown that the addition of three-body terms improves the accuracy of the components and the total energies. For a compact representation, three-body corrections can be incorporated into two-body interactions to reduce the complexity of the analysis. The method is applied to solvated alkali and halide ions, a nanocrystal of ice, and a Trp-cage protein (PDB: 1L2Y)-ligand complex.