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.