  In earlier papers, it is found that the Ricci scalar behaves in dual manner
(i) like a matter field and (ii) like a geometrical field. Using dual role of
the Ricci scalar, inhomogeneous cosmological models are derived. The essential
features of these models is capability of these to exhibit gravitational effect
of compact objects also in an expanding universe. Here, production of spinless
and spin-1/2 particles are demonstrated in these models.
