Structural and dynamic origin of the boson peak in a Cu-Zr metallic glass

Abstract

Using molecular dynamics simulations, we studied the short-time dynamics of the amorphous Cu${}_{50}$Zr${}_{50}$ alloy. We determined the occurrence of a well-defined boson peak in agreement with experimental observations. Our results indicate that the structural origin of the boson peak can be related to Cu and Zr atoms having large mean-square amplitudes in low-density defective local structures. Moreover, we show that these structural motifs display quasilocalized modes that resonantly couple with transverse phonons, leading to the accumulation of the low-energy modes around the boson peak. Finally, the correlation between the attenuation of sound and the boson peak is discussed.