Dynamic properties and Debye temperatures of bulk Au and Au clusters studied using extended x-ray-absorption fine-structure spectroscopy

The L₃ edge of bulk Au has been studied using x-ray-absorption spectroscopy in the temperature range 16--300 K. An effective Debye temperature of 165 K is derived from the thermal behavior of the extended x-ray absorption fine-structure Debye-Waller factors. Their behavior is also calculated for finite systems by using a free-bounded-sphere density of states and a Debye approximation for the phonon spectra. An excellent agreement is found with experimental data previously reported on Au clusters with mean diameters ranging from 15 to 43 A. This confirms that the dynamic properties of Au clusters are well described by a liquid-drop model in agreement with heat-capacity measurements.