Instead of scalar tensor gravity models which is applicable for description
of cosmic inflation with unknown dark sector of matter/energy, at presentense
there are presented different alternative scalar tensor vector gravities where
meaningful dynamical vector fields can support cosmic inflation well without to
use dark matter/energy concept. One of these gravity models was presented by
Moffat which its modified Schwarzschild black hole solution is used to study
thermodynamic phase transition in presence of the AdS space pressure in this
article. To do so we obtained an equation of state which asymptotically reaches
to equation of state of ideal gas for large black holes but for small scale
black holes we obtained a critical point at phase space where the black hole
can be exhibit with a phase transition at processes of isotherm and isobaric.
By looking at diagrams of the Gibbs free energy and the heat capacity at
constant pressure which are plotted versus the temperature and the specific
volume one can see an inflection point which means that the phase transition is
type of second order. In fact there is small to large phase transition for the
black hole which is equivalent to the Van der Waals liquid-gas phase transition
in ordinary thermodynamic systems. The phase transition is happened below the
critical point in phase space when the gravitational charge of the black hole
is equal to its mass.Comment: 21 pages, 4 figure