  We investigate phase transitions and critical phenomena of four dimensional
dyonic charged AdS black holes in the framework of thermodynamic geometry. In a
mixed canonical grand canonical ensemble with a fixed electric charge and
varying magnetic charge these black holes exhibit liquid gas like first order
phase transition culminating in a second order critical point similar to the
Van der Waals gas. We show that the thermodynamic scalar curvature R for these
black holes follow our proposed geometrical characterization of the R-crossing
Method for the first order liquid gas like phase transition and exhibits a
divergence at the second order critical point. The pattern of R crossing and
divergence exactly corresponds to those of a Van der Waals gas described by us
in an earlier work.
