The contribution of hydrogen atoms oscillations in Palladium in pair interaction H-H is calculated, The interpolation formula for an electronic chemical potential of a hydrogen subsystem containing only two energy parameter is obtained. It is shown that the approximation of an mean field for the configuration contribution to a chemical potential with renormalized due to oscillations to energy parameters with allowance for of electronic contribution satisfactorily describes an equilibrium of phases in a system a palladium-hydrogen. (C) 2002 Published by Elsevier Science Ltd on behalf of the International Association for Hydrogen Energy.