CALCULATION OF THE SPECTRAL DENSITIES OF THE SURFACE ALLOY SYSTEM (PTCCU1-C)(1) CU(100)/

A formalism for calculating the mean spectral densities of the disorde red surface alloy system (PtcCu1-c)(1)/Cu(100), is presented, using si multaneously the matching and the Green functions methods. The surface vibrational dynamics are developed using an effective field approach that goes in principle beyond the mean field approximation. Describing the surface layer (PtcCu1-c) by a random distribution of Pt and Cu at oms, we present numerical results for surface spectral densities,;ind surface mean-square displacements in this system, as a function of the defect concentration c (0 less than or equal to c less than or equal to 1).