  Considering the unexpected similarity between the thermodynamic features of
charged AdS black holes and that of the van der Waals fluid system, we
calculate the number densities of black hole micromolecules and derive the
thermodynamic scalar curvature for the small and large black holes on the
co-existence curve based on the so-called Ruppeiner thermodynamic geometry. We
reveal that the microscopic feature of the small black hole perfectly matches
that of the ideal anyon gas, and that the microscopic feature of the large
black hole matches that of the ideal Bose gas. More importantly, we investigate
the issue of molecular potential among micromolecules of charged AdS black
holes, and point out explicitly that the well-known experiential Lennard-Jones
potential is a feasible candidate to describe interactions among black hole
micromolecules completely from a thermodynamic point of view. The behavior of
the interaction force induced by the Lennard-Jones potential coincides with
that of the thermodynamic scalar curvature. Both the Lennard-Jones potential
and the thermodynamic scalar curvature offer a clear and reliable picture of
microscopic structures for the small and large black holes on the co-existence
curve for charged AdS black holes.
