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Calculation of surface binding energy for hydrogen, oxygen, and carbon atoms on metallic surfaces
A130 Surface Science 182 (1987) 85-97 North-Holland, Amsterdam
85
CALCULATION OF SURFACE BINDING ENERGY FOR HYDROGEN, OXYGEN, AND C A R B O N ATOMS ON METALLIC SURFACES Karl W. FRESE, Jr. Materials Research Laboratory, SRI International, Menlo Park, CA 94025, USA Received 12 August 1986; accepted for publication 28 October 1986
The model of Polar Covalence developed by Sanderson was used to calculate binding energies at zero coverage for H, O, and C atoms adsorbed on metal surfaces, For 11 single crystal metals, the average absolute difference between the experimental and calculated binding energies of hydrogen atoms was 3 - 4 kcal/mol, The model correctly predicts the weak binding of H on sp metals, e.g., Hg and Cd. Very similar agreement, 3 - 4 kcal/mol, was obtained for O atoms on 8 single crystal metals. In the case of carbon atoms, the binding energy on Ru and Ni was calculated to be less than the atomization energy of graphite, in agreement with experiment. A similar effect on Pd surfaces is predicted. The calculated low binding energy, 40 kcal/mol, of H atoms on top of .Pd is supported by a combination of thermodynamic, q u a n t u m mechanical, spectroscopic and thermal desorption data. These calculations represent the first attempt to apply Sanderson's method to first, second, and third row transition metals and to surface thermodynamics.
98
Surface Science 182 (1987) 98-124 North-Holland, A m s t e r d a m
A MOLECULAR DYNAMICS STUDY OF THE BEHAVIOUR OF XENON PHYSISORBED ON Pt(lll): COVERAGES LESS THAN ONE MONOLAYER John E. B L A C K Department of Physics, Brock Unwersity, St. Catharines, Ontario, Canada L2S 3A 1
and P. BOPP lnstitut )~r Physikalische Chemic L Technische Hochschule, D-6100 Darmstadt, Fed. Rep. of Germany Received 5 Augustus 1986; accepted for publication 9 October 1986 In recent He beam studies of Xe adsorbed on Pt(111) at less than monolayer coverages the xenon has been found to exist in incommensurate and commensurate phases both rotated by 30 ° with respect to the substrate. We present here molecular dynamics studies of small rafts of xenon particles on Pt(lll). We find evidence that the corrugation of the x e n o n - p l a t i n u m potential of interaction can read to an incommensurate phase but that, using reasonable interaction potentials, the corrugation cannot lead to a commensurate phase which can exist over a range of temperatures. A variety of molecular dynamic studies of raft behaviour are presented.
85
CALCULATION OF SURFACE BINDING ENERGY FOR HYDROGEN, OXYGEN, AND C A R B O N ATOMS ON METALLIC SURFACES Karl W. FRESE, Jr. Materials Research Laboratory, SRI International, Menlo Park, CA 94025, USA Received 12 August 1986; accepted for publication 28 October 1986
The model of Polar Covalence developed by Sanderson was used to calculate binding energies at zero coverage for H, O, and C atoms adsorbed on metal surfaces, For 11 single crystal metals, the average absolute difference between the experimental and calculated binding energies of hydrogen atoms was 3 - 4 kcal/mol, The model correctly predicts the weak binding of H on sp metals, e.g., Hg and Cd. Very similar agreement, 3 - 4 kcal/mol, was obtained for O atoms on 8 single crystal metals. In the case of carbon atoms, the binding energy on Ru and Ni was calculated to be less than the atomization energy of graphite, in agreement with experiment. A similar effect on Pd surfaces is predicted. The calculated low binding energy, 40 kcal/mol, of H atoms on top of .Pd is supported by a combination of thermodynamic, q u a n t u m mechanical, spectroscopic and thermal desorption data. These calculations represent the first attempt to apply Sanderson's method to first, second, and third row transition metals and to surface thermodynamics.
98
Surface Science 182 (1987) 98-124 North-Holland, A m s t e r d a m
A MOLECULAR DYNAMICS STUDY OF THE BEHAVIOUR OF XENON PHYSISORBED ON Pt(lll): COVERAGES LESS THAN ONE MONOLAYER John E. B L A C K Department of Physics, Brock Unwersity, St. Catharines, Ontario, Canada L2S 3A 1
and P. BOPP lnstitut )~r Physikalische Chemic L Technische Hochschule, D-6100 Darmstadt, Fed. Rep. of Germany Received 5 Augustus 1986; accepted for publication 9 October 1986 In recent He beam studies of Xe adsorbed on Pt(111) at less than monolayer coverages the xenon has been found to exist in incommensurate and commensurate phases both rotated by 30 ° with respect to the substrate. We present here molecular dynamics studies of small rafts of xenon particles on Pt(lll). We find evidence that the corrugation of the x e n o n - p l a t i n u m potential of interaction can read to an incommensurate phase but that, using reasonable interaction potentials, the corrugation cannot lead to a commensurate phase which can exist over a range of temperatures. A variety of molecular dynamic studies of raft behaviour are presented.