  Dispersion interactions are one of the components of van der Waals (vdW)
forces, which play a key role in the understanding of intermolecular
interactions in many physical, chemical and biological processes. The theory of
dispersion forces was developed by London in the early years of quantum
mechanics. However, it was only in the 1960s that it was recognized that for
molecules lacking an inversion center such as chiral and helical molecules,
there are chirality-sensitive corrections to the dispersion forces proportional
to the rotatory power known from the theory of circular dichroism and with the
same distance scaling law R-6 as the London energy. The discovery of the
Chirality-Induced Spin Selectivity (CISS) effect in recent years has led to an
additional twist in the study of chiral molecular systems, showing a close
relation between spin and molecular geometry. Motivated by it, we propose in
this investigation to describe the mutual induction of charge and spin-density
fluctuations in a pair A-B of chiral molecules by a simple physical model. The
model assumes that the same fluctuating electric fields responsible for vdW
forces can induce a magnetic response via a Rashba-like term, so that an
spin-orbit field acting on molecule B is generated by the electric field
arising from charge density fluctuations in molecule A (and viceversa). Within
a second-order perturbative approach, these contributions manifest as an
effective intermolecular exchange interaction. Although expected to be weaker
than the standard London forces, these interactions display the same R$^6$
distance scaling.
