  In the study of many-particle systems both the interaction of particles can
be essential and such feature as their internal (composite) structure. To
describe these aspects, the theory of deformed oscillators is very efficient.
Viewing the particles as p,q-deformed bosons, in the corresponding p,q-Bose gas
model we obtain in explicit form virial expansion along with the 2nd to 5th
virial coefficients. The obtained virial coefficients depend on the deformation
parameters p,q in the form symmetric under p<->q, and at p->1, q->1 turn into
those known for usual bosons. Besides real parameters, we analyze the case of
complex mutually conjugate p and q and find interesting implications. Also, the
critical temperature is derived (for the p,q-Bose gas) and compared with the
T_c of standard case of Bose condensation. Similar results are presented for
the deformed Bose gas model of the Tamm-Dancoff type.
