Random Phase Approximation Applied to Many-Body Noncovalent Systems

The random phase approximation (RPA) has received considerable
interest in the field of modeling systems where noncovalent interactions
are important. Its advantages over widely used density functional
theory (DFT) approximations are the exact treatment of exchange and
the description of long-range correlation. In this work, we address
two open questions related to RPA. First, we demonstrate how accurately
RPA describes nonadditive interactions encountered in many-body expansion
of a binding energy. We consider three-body nonadditive energies in
molecular and atomic clusters. Second, we address how the accuracy
of RPA depends on input provided by different DFT models, without
resorting to self-consistent RPA procedure, which is currently impractical
for calculations employing periodic boundary conditions. We find that
RPA based on the SCAN0 and PBE0 models, that is, hybrid DFT, achieves
an overall accuracy between CCSD and MP3 on a data set of molecular
trimers from Řezáč et al. (J. Chem. Theory. Comput. 2015, 11, 3065).
Finally, many-body expansion for molecular clusters and solids often
leads to a large number of small contributions that need to be calculated
with high precision. We therefore present a cubic-scaling (or self-consistent
field (SCF)-like) implementation of RPA in atomic basis set, which
is designed for calculations with high numerical precision.