Capillary-wave roughening of surface-induced layering in liquid gallium

The temperature dependence of surface-induced atomic layering in liquid gallium has been investigated with x-ray reflectivity. The prominent layering peak at ${\mathit{q}}_{\mathit{z}}$=2.4 A${\mathrm{̊}}^{\mathrm{-}1}$ decreases dramatically upon heating from 22 to 170 °C, but its width stays, unexpectedly, unchanged. The decrease is traced to the temperature dependence of capillary-wave induced surface roughness. The constant width indicates a temperature-independent layering decay length. The measured layering amplitudes are found to be significantly underestimated by existing theory and molecular simulations. © 1996 The American Physical Society.