  In some quantum chemical applications, the potential models are linear
combination of single exactly solvable potentials. This is the case equivalent
of the Stark effect for a charged harmonic oscillator (HO) in a uniform
electric field of specific strength (HO in an external dipole field). We obtain
the exact s-wave solutions of the Dirac equation for some potential models
which are linear combination of single exactly solvable potentials (ESPs). In
the framework of the spin and pseudospin symmetric concept, we calculate the
analytic energy spectrum and the corresponding two-component upper- and
lower-spinors of the two Dirac particles by the Nikiforov-Uvarov (NU) method,
in a closed form. The nonrelativistic limit of the solution is also studied and
compared with the other works.
