Determination of the structure of disordered overlayers of ethylene on clean and hydrogen-covered Pd(1 1 1) by low-energy electron diffraction

The surface structure of the disordered overlayer formed by ethylene adsorption on Pd(1 1 1) at 80 K is determined by low-energy electron diffraction (LEED) from the effects of chemisorbed molecules on the intensity versus beam energy (I/E) variation of the substrate (1×1) Bragg spots. It is shown that ethylene is di-σ-bonded on clean Pd(1 1 1), where the measured geometry is in agreement with the results of previous density functional theory (DFT) calculations. The structure of a disordered overlayer of ethylene on hydrogen-covered Pd(1 1 1) at 80 K is also measured using LEED and is found to form a π-bonded species in accord with previous infrared results.