Energy dispersion curves of the surface phonons of the (111) surface were measured by using high resolution electron energy loss spectroscopy. Two large loss peaks and three small loss peaks in the specular spectra and several branches in the off-specular spectra were found. On the basis of lattice dynamics calculations using bulk parameters, the theoretical phonon dispersion curves of the unrelaxed surface were obtained. One vibrational mode appeared above the bulk phonon bands; which indicated stiffening of the B-B bonds of the surface octahedra.

Surface Phonon Dispersion Curves of the LaB6(111) Surface. Rokuta, E., Yamamoto, N., Hasegawa, Y., Nagao, T., Trenary, M., Oshima, C., Otani, S.: Surface Science, 1996, 357-358, 712-6