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Other Experimental Evidence for Metallic Binding

A difference of two orders of magnitude has been measured in the DC conductivity of AU55 and Aufj at 100 K [29,30]. From this, and the MES observation [46] that the total electron count in the metal core of Au s may be about 2 less than in AU55, it would appear that there is a very nonuniform distribution of levels, with a much larger energy splitting for the HOMO level of Au j than for AU55. Furthermore, the density of states in these levels must be very low. [Pg.21]

By studying the AU55 system by means of PNMR, one would hope to be able to obtain additional microscopic information about the electronic behavior. Unfortunately, NMR experiments proved to be non-trivial [29], since the resonance was extremely weak. This has been taken as an indication that metallic shielding may still be incomplete. [Pg.21]

The main result extracted from P NMR was that the AU55 clusters do not exhibit a normal Korringa relation. Rather, there is an indication of the sort of general two-level behavior often seen in disordered glassy systems. This does not appear to be in disagreement with the results reported above, especially when one considers the modification of the intra-cluster energy levels due to the intercluster interactions. [Pg.21]

If metallic conductivity within the cluster should be present, with mobile, delocalized electrons, one might hope to see a linear electronic term in the specific heat [54, 56]. Considering the results above, such a linear term should not be expected for AU55. [Pg.22]

The T phonon term [25], corresponding to the center-of-mass motion of the clusters, can be safely extrapolated for temperatures below 2 K, and the linear term can be estimated from the known value of 7 for bulk gold [142] in the same temperature range. These two terms would be approximately equal for a temperature of about 40 mK. [Pg.22]


See other pages where Other Experimental Evidence for Metallic Binding is mentioned: [Pg.20]   


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