Topography and surface melt on spherical gold crystals after purification by a pre-melt in air

Melting of icosahedral gold nanoclusters from molecular dynamics simulations

“…Simulations 18 and experiments 19 on bulk slab-like geometries with exposed {111} surfaces have shown that, unlike the {100} and {110} surfaces which melt below the bulk melting temperature T m , the {111} surface is a nonmelting surface without roughening, wetting, or melting up to the bulk melting temperature T m , and can in fact lead to superheating of the solid 20 . In light of this observation it is interesting to consider how the high stability of the {111} facets effects the melting and equilibrium shape of such icosahedral clusters.…”

Surface reconstruction precursor to melting in Au309 clusters

“…Previous simulations 21 and experiments 22 on slablike geometries have shown that the (111) surface is a nonmelting surface without roughening, wetting, or melting up to the bulk melting temperature, which can lead to superheating of the solid. 23 However, the behavior of the Q 6 parameter for the Ih cluster is different and unexpected in this observation. The Q 6 parameter values for surface and interior atoms of the Ih cluster start from a surface (0.206) and bulk (0.155) values at 100K.…”

Surface Analysis and Structures Spherical Crystals of Very Clean Au, Cu and Au-Cu Alloys Grown from a Drop of Melt

“…AES showed, apart from the gold signals, a strong carbon peak (272 eV) and a small silicon peak (92 eV). The crystals had a comparatively rough surface [2], Purification was possible by melting the gold in air. In a temperature gradient spherical gold crystals grow in air with quite smooth surfaces.…”

“…AES was performed without any further melting or after remelting and solidification on spectral graphite in 10~7 Pa. In both cases the carbon peak was lowered by a factor 1/5, the silicon peak had dissappeared, and in spite of melting in air no nitrogen or oxygen peaks or other ones were detected [2]. A peak at 150eV does not belong to sulphur but to gold because its intensity fits to the other Au peaks.…”

“…The low indexed flats (111) and (001) and the other curved areas are smooth at least in light-optical sense [1]. Alloying Au with 100 at ppm Cu destroys this smoothness [7], In order to check the cleanliness by an other method we have started Auger electron spectroscopy (AES) with a four grid retarding field analyser (Vacuum Generators), with primary electrons up to 4 keV and suitable modulations between 2 and 6 V. In the present work former investigations on purified gold [2] are extended to copper and to Au-Cu alloys. Electron diffraction in this system is reported additionally.…”