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We report here a Monte Carlo study of the thennodynamic and structural properties of a two-dimensional system of 2500 particles interacting by a repulsive inverse sixth power potential. Particular effort was made in the melting region, both to identify the defect structures and to ascertain the thennodynamic changes associated with the transition. Significant precursor fluctuations occurred on both the solid and fluid sides, and the unbinding of dislocation pairs was observed on melting. More complex defect patterns, including grain boundary loops, were also generated near melting. The Kosterlitz-Thouless, Halperin-Nelson, and Young dimensionless elastic constant approached the universal value 161T in the solid, and the orientational correlation range tended to diverge in the fluid near freezing. However, we were unable to distinguish between a very weak (.:I V IV ",,0.7%) first order and a continuous transition, since both spatial structures and temporal relaxations became exceedingly long.

The (001) surfaces of AuGa2 and AuInz intermetallic compounds were studied with use of synchrotron-radiation-excited angle-resolved photoemission.Spectra collected for photoelectron emission normal to the sample surfaces were used to map the E versus k dispersion relation of both compounds along the 6 symmetry line of the bulk Brillouin zone. The results show that the Au Sd bands of each compound are relatively flat, but the splittings of the bands at point I are nearly the same as for elemental Au. A surface state was also observed on each surface in a band-gap region about 6 eV below the Fermi levels of the two compounds.

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