Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite
2018
Tamtögl, Anton | Sacchi, M. | Calvo-Almazán, I. | Zbiri, M. | Koza, M.M. | Ernst, W.E. | Fouquet, P.
We present a combined experimental and theoretical study of the self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed ammonia, NH₃, on graphite. Together with van der Waals corrected density functional theory calculations we show that the diffusion of NH₃ follows a hopping motion on a weakly corrugated potential energy surface with an activation energy of about 4 meV which is particularly low for this type of diffusive motion. The hopping motion includes further a significant number of long jumps and the diffusion constant of ammonia adsorbed on graphite is determined with D=3.9⋅10−8m2/s at 94 K.
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