The structure and phase behaviour of the clean Pt(111) surface was studied between 300K and 0.92Tm via X-ray scattering. The surface was unreconstructed at homologous temperatures of below 0.65. For higher homologous temperatures 0.65, it was found that the top layer underwent a continuous commensurate-incommensurate transformation into a translationally and orientationally disordered discommensuration-fluid phase, which was isotropically compressed relative to the bulk (111) planes. A disordered arrangement of discommensurations separated regions of ideal face-centered-cubic ABC stacking from regions of faulted ABA stacking. As the temperature was increased, the compression of the surface layer increases and the incommensurability follows a power-law versus reduced temperature with an exponent equal to 1/3. For temperatures increasing above 0.75Tm, sixfold orientational ordering of the discommensurations develops and increases.

Reconstruction of the Pt(111) Surface - X-Ray-Scattering Measurements. G.Grübel, K.G.Huang, D.Gibbs, D.M.Zehner, A.R.Sandy, S.G.J.Mochrie: Physical Review B, 1993, 48, 18119-39