  Mutual Coulomb interactions between electrons lead to a plethora of
interesting physical and chemical effects, especially if those interactions
involve many fluctuating electrons over large spatial scales. Here, we identify
and study in detail the Coulomb interaction between dipolar quantum
fluctuations in the context of van der Waals complexes and materials. Up to
now, the interaction arising from the modification of the electron density due
to quantum van der Waals interactions was considered to be vanishingly small.
We demonstrate that in supramolecular systems and for molecules embedded in
nanostructures, such contributions can amount to up to 6 kJ/mol and can even
lead to qualitative changes in the long-range vdW interaction. Taking into
account these broad implications, we advocate for the systematic assessment of
so-called Coulomb singles in large molecular systems and discuss their
relevance for explaining several recent puzzling experimental observations of
collective behavior in nanostructured materials.
