Figure11

Figure 11. Resulting anisotropy of the relative thermal vibrations, $$\gamma =⟨{\mathrm{\Delta }{u}_{\mathrm{\perp }}}^2⟩/⟨{\mathrm{\Delta }{u}_{\parallel }}^2⟩$$: experimental data (circles) and corresponding best-fit Einstein model (solid line). Error bars have been omitted for clarity.