We have performed electronic structure calculations of the interaction of potassium and oxygen with graphite (GR), individually and as coadsorbates. We use up to three graphite planes to represent the graphite surface, but we show that the main physics is correctly described by a single graphite layer. At low coverage the potassium–graphite bond is largely ionic, and the variation of the K–GR bond energy with the lateral position of the K atom in the graphite unit cell is very small. We study the interaction between atomic oxygen and graphite. We find that O binds strongest at the bridge site, but the barrier for diffusion is rather small. The frequency for the perpendicular O–graphite vibrational mode is remarkably low (53 meV), reflecting the relative slow variation of the O–graphite interaction energy with the separation between the O atom and the graphite surface. We consider the adsorption of on a clean graphite surface and on a graphite surface with a low concentration of potassium. On the clean surface the –graphite interaction is found to be repulsive (the weak attractive van der Waals interaction is not included in our theoretical method), in accordance with the extremely low sticking coefficient observed for on clean graphite. When potassium is adsorbed on the graphite surface, chemisorbs at the potassium sites which is consistent with the large sticking coefficient observed for on a potassium covered surface. The energy barrier towards dissociation of on the clean graphite surface is estimated to be similar to that of gas phase For on K/graphite we find that chemisorbs “side-on” K, and that the barrier for dissociation is much smaller than in the gas phase or on the clean graphite surface.
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22 February 1998
Research Article|
February 22 1998
Adsorption of potassium and oxygen on graphite: A theoretical study
D. Lamoen;
D. Lamoen
Department of Physics, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
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B. N. J. Persson
B. N. J. Persson
Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6032
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J. Chem. Phys. 108, 3332–3341 (1998)
Article history
Received:
September 30 1997
Accepted:
November 14 1997
Citation
D. Lamoen, B. N. J. Persson; Adsorption of potassium and oxygen on graphite: A theoretical study. J. Chem. Phys. 22 February 1998; 108 (8): 3332–3341. https://doi.org/10.1063/1.475732
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