Structure of physisorbed molecules on an oxide surface from potential calculations and dynamical low-energy electron diffraction analysis: Acetylene on MgO(100)

Semiempirical potential calculations have been combined with a dynamical low-energy electron diffraction analysis to determine the complete structure of molecules physisorbed on an oxide surface, namely, acetylene (C2H2) adsorbed on MgO(100) at T = 88 K. This allows determination of the adsorption sites and the molecule-molecule and molecule-substrate distances. The results are consistent with molecules that lie almost parallel to the surface in a herringbone structure. Neither molecule nor substrate exhibits significant distortions, due to the weak physisorption.