Efficient Scheme for Calculation of Low-Energy Electron-Diffraction Intensities in the Presence of Large Superlattices, with Application to the Structural Analysis of Benzene Adsorbed on Rh(111)

A powerful calculational low-energy electron-diffraction scheme is introduced for super lattices with unit cells of any size: beam-set neglect. It is applied in the first structural analysis from low-energy electron-diffraction intensities of a large molecule, benzene, adsorbed on a single-crystal metal surface, Rh(111). In a $\left({3,1}{1,3}\right)$ lattice, benzene is found to lie flat on the surface, centered over hcp-type hollow sites. A planar, possibly distorted ${\mathrm{C}}_{6}$ ring is found with Rh-C bond lengths of 2.35\ifmmode\pm\else\textpm\fi{}0.05 \AA{}.