  We present a mean field approach based on pairs of fermionic atoms to
describe condensates in the BEC-BCS crossover regime. By introducing an
effective potential, the mean field equation allows us to calculate the
chemical potential, the equation of states and the atomic correlation function.
The results agree surprisingly well with recent quantum Monte Carlo
calculations. We show that the smooth crossover from the bosonic mean field
repulsion between molecules to the Fermi pressure among atoms is associated
with the evolution of the atomic correlation function.
