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Geometric and electronic factors determining the difference in
reactivity of H2 on Cu(100) and Cu(111)

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Geometric and electronic factors determining the difference in
reactivity of H2 on Cu(100) and Cu(111)

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by Peter Kratzer, BjÃ¸rk Hammer and Jens K. NÃ¸rskov Surface Science 359,
45 (1996).

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Abstract

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We present a comparative density functional theory study of H2
dissociation over Cu(100) and Cu(111) surfaces. For like reaction
geometries we find that the more open (100) surface is the more reactive
as is expected from usual arguments for the electronic effects in metal
surface reactivity theory. However, when allowing for different reaction
geometries, we find that the minimum energy barrier is 0.1 eV larger
over the (100) surface compared to over the (111) surface. The larger
barrier correlates with a more stretched H-H bond in the transition
state and with further separated final hollow sites for the atomic H on
the (100) surface compared to the (111) surface. Consequently, we assign
the minimum energy barrier ordering to geometrical effects. Finally,
using a simple model of the sticking dynamics, the calculated difference
in barrier heights over the two facets is discussed in relation to the
difference in onset of hydrogen sticking as measured in molecular beam
experiments.

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