Insights from calculated phonon dispersion curves for an overlayer of H on Pt(111)

SURFACE SCIENCE

卷:587

Article; Proceedings Paper

Hong, SY ; Rahman, TS ; Heid, R ; Bohnen, KP

关键词: hydrogen;    platinum;    low index single crystal surfaces;    surface phonons;    surface phonon dispersion;    surface electronic structure;    surface force constants;   

DOI  :  10.1016/j.susc.2005.04.031

来源: Elsevier

【 摘 要 】

We have calculated the dispersion curves of H vibrational modes on Pt(111), using first-principles, total energy calculations based on a mixed-basis set and norm-conserving pseudopotentials. Linear response theory and the harmonic approximation are invoked. For I ML coverage with H atoms in the fcc hollow sites, we find modes at 73.5 meV and 142.6 meV, polarized, respectively, parallel and perpendicular to the surface, at the F point of the surface Brillouin zone. The degeneracy of the parallel mode is lifted at the zone boundaries, yielding modes at 69.6 meV and 86.3 meV, at the M point, and at 79.4 meV and 80.8 meV, at the K point. The changes in Pt surface force constant on H adsorption are found to shift the frequencies of the substrate surface modes from their calculated values for clean Pt(111). We also consider the case of subsurface adsorption for 2 ML of H and present vibrational frequencies of H atoms adsorbed in several subsurface sites. The appearance of new vertically polarized H modes in the range 98106 meV (octahedral site occupancy) and 124-162 meV (tetrahedral site occupancy) is discussed in the context of experimental data. (c) 2005 Elsevier B.V. All rights reserved.

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