  We study thermodynamics and geometrothermodynamics of a particular black hole
configuration with a nonlinear source. We use the mass as fundamental equation,
from which it follows that the curvature radius must be considered as a
thermodynamic variable, leading to an extended equilibrium space. Using the
formalism of geometrothermodynamics, we show that the geometric properties of
the thermodynamic equilibrium space can be used to obtain information about
thermodynamic interaction, critical points and phase transitions. We show that
these results are compatible with the results obtained from classical black
hole thermodynamics.
