A REAL-SPACE MULTIPLE-SCATTERING THEORY OF LOW-ENERGY ELECTRON-DIFFRACTION - A NEW APPROACH FOR THE STRUCTURE DETERMINATION OF STEPPED SURFACES

A new theory of Low Energy Electron Diffraction (LEED) is presented in which the relevant multiple scattering equations are solved in the angular momentum representation within the framework of real-space multiple scattering theory (RS-MST). This approach avoids the plane wave basis used in many conventional LEED techniques and its associated limitations when applied to the calculation of LEED intensities from open surfaces containing small bulk interplanar spacings. In particular, high Miller index, stepped surfaces which lie beyond the present capabilities of conventional LEED, can now be treated in a relatively efficient and convergent manner. The new theory is tested by evaluating I-V spectra from the (100), (311), (331) surfaces of Cu which are compared with the results of a layer doubling (LD) LEED calculation. Excellent agreement is obtained in the (100) and (311) cases, for which the LD approach is expected to be applicable. The (311) surface is about the highest index fcc surface which can reasonably be attempted with the existing approaches. The results obtained for the case of the (331) surface using the LD and the RS-MST approaches agree up to about E = 100 eV, beyond which the LD process fails to converge. We discuss and contrast the convergence properties of both methods. © 1990.