Benchmark of Excitation Energy Shifts from Frozen-Density Embedding Theory: Introduction of a Density-Overlap-Based Applicability Threshold

We
present a thorough investigation of the errors in results obtained
with the combination of frozen-density embedding theory and the algebraic
diagrammatic construction scheme for the polarization propagator of
second order (FDE-ADC(2)). The study was carried out on a set of 52
intermolecular complexes with varying interaction strength, each consisting
of a chromophore of fundamental interest and a few small molecules
in its environment. The errors emerging in frozen-density embedding
theory-based methods originate from (a) the solver of the quantum
many-body problem used to obtain the embedded wave function (ΨAemb), (b) the approximation
for the explicit density functional for the embedding potential, and
(c) the choice of the density representing the environment (ρB(r⃗)). The present work provides a
comprehensive analysis of the errors in the excitation energies based
on the last two factors. Furthermore, a density-overlap-based parameter
is proposed to be used as an a priori criterion of applicability.