  The Interacting Quantum Atoms (IQA) electronic energy partition is an
important method in the field of quantum chemical topology which has given
important insights of different systems and processes in physical chemistry.
There have been several attempts to include Electron Correlation (EC) in the
IQA approach, for example, through DFT and Hartree-Fock/Coupled-Cluster (HF/CC)
transition densities. This work addresses the separation of EC in Fermi and
Coulomb correlation and its effect upon the IQA analysis by taking into account
spin-dependent one- and two-electron matrices $D^{\mathrm{HF/CC}}_{p\sigma q
\sigma}$ and $d^{\mathrm{HF/CC}}_{p\sigma q\sigma r\tau s\tau}$ wherein
$\sigma$ and $\tau$ represent either of the $\alpha$ and $\beta$ spin
projections. We illustrate this approach by considering BeH$_2$,BH, CN$^-$, HF,
LiF, NO$^+$, LiH, H$_2$O$\cdots$H$_2$O and C$_2$H$_2$, which comprise non-polar
covalent, polar covalent, ionic and hydrogen bonded systems. The same and
different spin contributions to ($i$) the net, interaction and
exchange-correlation IQA energy components and ($ii$) delocalisation indices
defined in the quantum theory of atoms in molecules are carefully examined and
discussed. Overall, we expect that this kind of analysis will yield important
insights about Fermi and Coulomb correlation in covalent bonding,
intermolecular interactions and electron delocalisation in physical chemistry.
