DIFFUSE LEED INTENSITY CALCULATIONS TAKING INTO ACCOUNT THE PAIR CORRELATION EFFECTS IN PARTIALLY ORDERED OVERLAYER

The elastic diffuse intensity of electrons scattered by a short-range-ordered adlayer depends on the structure factors and on renormalized t matrices for each kind of occupied bonding sites. In many cases, the computation of these structure factors is a crucial point for the application of the general DLEED theory. Their determination necessitates the knowledge of the site-occupancy pair correlation functions. Up to now two procedures removing pair correlation effects from the data have been used for DLEED intensity calculations. The first procedure, the Y-function method, can be applied only in the particular case where there is one kind of chemisorption site. The second one was proposed recently and is based on the sampling of diffuse LEED intensity distributions by conventional spot intensities. The aim of this paper is to study DLEED intensity distribution coming from the sampling method and from the general treatment of DLEED taking into account the pair correlation effects. We take as an example the Pt(111)/CO system. The site-occupancy pair correlation functions of CO adsorbed on Pt(111) are obtained by a Monte Carlo simulation. DLEED intensities are analyzed using the energy-dependent I–V curves.