The Structure of Dodecanamide Monolayers Adsorbed on Graphite

摘要

A combination of synchrotron X-ray and neutron diffraction have been used to characterise the sub-monolayer (low-coverage) crystalline structure of dodecanamide [CH_3-(CH_2)(_io)-CONH_2] adsorbed on graphite. The calculated struc ture reveals that the molecules lie flat on the graphite surface. The amide head-groups hydrogen-bond into dimers, and, significantly, adjacent dimers form further hydrogen bonds yielding extended chains in good agreement with previous STM results. This monolayer has a very high stability, as observed in its melting point which is significantly higher than the bulk melting point even at these low coverages. The characteristics of the hydrogen bonds are found to be in close agreement with those reported in the bulk crystals. The cov erage dependence of the structure is discussed.