Multilayer relaxation on clean Pd{311} has been determined by analysis of low-energy-electron-diffraction intensity data collected from a sample at -140 °C. The results, in terms of changes Δ${\mathit{d}}_{\mathit{i}\mathit{k}}$ from the bulk value ${\mathit{d}}_{\mathrm{bulk}}$ (1.485 Å) of the interlayer spacing ${\mathit{d}}_{\mathit{i}\mathit{k}}$ between layers i and k, are as follows: Δ${\mathit{d}}_{12}$=(-0.21±0.03) Å or (-14.1±2.0)% of ${\mathit{d}}_{\mathrm{bulk}}$, Δ${\mathit{d}}_{23}$=(-0.03±0.03) Å or (-2.0±2.0)% of ${\mathit{d}}_{\mathrm{bulk}}$, Δ${\mathit{d}}_{34}$=(-0.01±0.05) Å or (-0.7±3.4)% of ${\mathit{d}}_{\mathrm{bulk}}$, and Δ${\mathit{d}}_{45}$=(0.08±0.05) Å or (+5.4±4.0)% of ${\mathit{d}}_{\mathrm{bulk}}$. Since the {311} surface has only one mirror line, parallel relaxations along the mirror line (the x direction) are possible and indeed found. The changes along x are Δ${\mathit{s}}_{12}^{\mathit{x}}$=(0.08±0.05)Å or (+3.0±1.9)% of the bulk value 2.626 Å, and Δ${\mathit{s}}_{23}^{\mathit{x}}$=(-0.05±0.05) Å or (-1.9±1.9)% of the bulk value. The contraction of ${\mathit{d}}_{12}$ is comparable in magnitude to that found on {311} surfaces of other face-centered-cubic metals, in contrast to the results obtained earlier on Pb{110}, Pb{001}, and Pb{111}. However, as on these low-index surfaces, the relaxations extend more deeply into the bulk than on surfaces of other fcc metals.

• Received 25 April 1991

DOI:https://doi.org/10.1103/PhysRevB.44.8267