Abstract
Elastic low-energy-electron-diffraction intensity-energy spectra are calculated for Ni (001), (110), and (111) surfaces between 10 and 220 eV by the layer-Korringa-Kohn-Rostoker method and compared with recent room-temperature experimental results. The calculation uses the Wakoh self-consistent muffin-tin potential, retains eight phase shifts, and includes finite temperature effects (assuming a Debye spectrum). An effective Debye temperature of 335°K is found from the temperature dependence of spectral intensities, an energy-dependent imaginary potential roughly of the form for electron energy (in eV) is determined by matching features of the calculated spectra to experiment, and the best values of the first interlayer spacing are found to be 1.76 Å (the bulk spacing) +0.02 ± 0.02 Å on the (001) surface, 1.24 - (0.06±0.02) Å on the (110) surface, and 2.03 - (0.025±0.025) Å on the (111) surface. With these parameters, excellent agreement with observed spectra is obtained in positions and shapes of peaks for several beams and a large number of incident angles. For all faces a small systematic deviation in peak positions is found with a constant 11-eV inner potential, suggesting an inner potential varying from the expected static value of 13.5 at low energies to about 9 eV near 220 eV. Comparison of relative intensities between calculation with the above and experiment suggests that excitation of electrons from Ni significantly enhances electron absorption above 65 eV.
- Received 10 July 1974
DOI:https://doi.org/10.1103/PhysRevB.11.1460
©1975 American Physical Society