Does the Boson Peaks Exist in Small Neutral Gold Clusters?

Abstract

The Boson peaks are typically ascribed to an excess density of vibrational states for the small clusters. A well resolved boson peak is observed in the low-frequency portion of the spectrum. A starting point for our discussion is the behaviour of the boson peak, derived from the vibrational density of states and the temperature dependencies of the vibrational heat capacities of the re-optimized neutral gold clusters. This Boson peak is associated with the existence of intermediate range order (IRO) in the arrangements of atoms. The low frequency (Far Infrared FIR, IR-C 200-10 cm−1) containing this dominant spectral line (Boson peak) is interpreted in terms of its relationship to the amplitude and extent of the density fluctuations in atoms and is, thereby, considered a measure of the intermediate range order in these atoms. We found a systematic relation among the boson peak energy, the boson peak intensity per atom, and the zigzag-bond density; the peak energy decreases and the peak intensity increases as zigzag-bond density decreases.