Spherically shaped crystals of gold were grown by solidification of a drop of melt in UHV. Their surfaces were investigated in situ by RHEED. The superstructures (001) (5x20) and (110) (1 X 2) were observed again. Further superstructures were found: on (001) vicinal planes, (227) (1 X 1), (111) (23 X 1) and (551)c(l X 1). Several of the new structures are related to structures already known.

Spherical Ag crystals were annealed a t 400 to 700 "C in oxygen (air) of lo-* and lot3 Torr.Diffraction of 60 keV electrons shows extra spots indicating two-dimensional adsorption structures on the poles (111) and (001) and their surroundings. The extended areas of both adsorption structures are faceted; they have developed circular terraces around (1 11) or (001). Contrary t o the faceting of copper the facets on silver are developed a t the highest temperature, they are connected with the adsorption structures of oxygen which lower the free surface energy selectively on the (111)-and (001)-poles. -Premelting of the high indexed surface planes was indicated by a "Red Area". Kugelformige Silberkristalle wurden bei 400 bis 700 "C in Sanerstoff (Luft) von 10-4 und lof3 Torr getempert. Die Beugung von 60 keV-Elektronen zeigt zusatzliche Reflexe; sie ruhren her von zweidimensionalen Adsorptionsstrukturen auf den Polen (111) und (001) und ihren Umgebungen. Die ausgedehnten Bereiche beider Strukturen sind facettiert, sic habcn Kreisterrassen urn (1 11) nnd (001) entwickelt. I m Gegensatz zur Facettierung von Kupfer entwickeln sich die Ag-Facetten bei der hochsten Temperatur ; sie sind verkniipft mit den Sauerstoff-Adsorptionsstrukturen, die die freie Oberflachenenergie selektiv auf den (111)-und (001)-Fliichen erniedrigen. -Ein Vorschmelzen der hoher indizierten Netzebenen wird angezcigt durch einen ,,Roten Bereich".

The reciprocal lattice of a periodic terrace-ledge surface is calculated by Fourier transformation. This formalism is applied to spherical crystals. In that case the reciprocal lattice consists of bundles of finite streaks; their vertices are situated on the reciprocal lattice points of the bulk crystal. That confirms a model formerly used to discuss LEED experiments with spherical crystals. The calculation is generalized to describe terraces composed of several monolayers.