The He surface reflection coefficients have been evaluated for the Pt(111) surface by using a long range force constants model for the bulk phonons. The lowering of the lateral surface force constants allows one to explain in a quantitative manner the existence of all the peaks observed in the experimental spectra.
The phonon frequencies of the (111) surface of Platinum: existence of three localized modes / Bortolani, Virginio; Franchini, Anna; Santoro, Giorgio. - In: SURFACE SCIENCE. - ISSN 0039-6028. - STAMPA. - 189-190:(1987), pp. 675-678. [10.1016/S0039-6028(87)80498-3]