Noncovalent interactions (NIs) play an important role in molecular biology, supramolecular chemistry, materials, and molecular crystals. The characterization and interpretation of NIs have remained a great challenge for experimentalists and theorists. In a previous work, Nguyen and coworkers [Nguyen, B. D. et al J. Chem. Theory Comput. 2020, 16 (4), 2258–2273.] developed the adiabatic connection symmetry-adapted perturbation theory (AC-SAPT) for nondegenerate dimers and established the importance of electrodynamic screening to understand NIs. The AC-SAPT series within the many-body perturbation theory (MBPT) spuriously diverges while AC-SAPT series within random phase approximation is always convergent. As follow-up to the previous work, I present an extension of the AC-SAPT formalism within dimers to N-monomers and establish the dispersion size-consistency condition which states that the total dispersion energy of a N-monomer system is independent of any partitioning into subsystem. The development of dipsersion size-consistency provides an additional condition to the Casimir-Polder size-consistency, which is evident in long-range dispersion interactions. Next, I explore disperion theories such as RPA, MBPT, and SAPT and determine which ones satisfy the dispersion size-consistency. Finally, dispersion energy calculations for RPA and MBPT are shown along with conclusions for electronic structure theory of NIs and future considerations for modeling NIs.

Dispersion size-consistency within the adiabatic connection symmetry-adapted perturbation theory

ACS Spring 2022

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