  Even though many scalar field models of dark energy have been considered in
the literature, there is another interesting class of dark energy models
involving a fluid known as a Chaplygin gas. In addition to describing the dark
energy, both scalar-tensor model and the Chaplygin gas model are suitable
candidates for explaining the spherical cosmological collapse. One of the most
well-known scalar field models is the quintessence model, which was first
introduced to explain an accelerating expanding universe. Using a special form
of the quintessence model that is equivalent to Chaplygin gas, we describe
evolution of a spherical collapse. We study the cosmological properties of the
quintessence field with a special potential. In addition to the quintessence
model, that can be converted into a Chaplygin gas model in a particular case,
we claim that the fixed-potential tachyonic model is equivalent to the
Chaplygin gas model. In this work, we obtain the spherical collapse parameters:
the virialized overdensity parameters, radius, the energy density at the
turnaround moment, etc. We compare the results of the proposed model with the
standard model of cosmology and the Einstein-de Sitter model. We show that the
formation of the large-scale structures within the framework of a Chaplygin gas
model happens earlier than predicted in the standard model.
