  By starting with a seed Newtonian potential-density pair we construct
relativistic thick spherical shell models for a Majumdar-Papapetrou type
conformastatic spacetime. As a simple example, we consider a family of
Plummer-Hernquist type relativistic spherical shells. As a second application,
these structures are then used to model a system composite by a dust disk and a
halo of matter. We study the equatorial circular motion of test particles
around such configurations. Also the stability of the orbits is analyzed for
radial perturbation using an extension of the Rayleigh criterion. The models
considered satisfying all the energy conditions.

General Relativity and Quantum Cosmology