Molecular Dynamics Study on Vibrational Motion of Amorphous and Liquid Zr<SUB>67</SUB>Ni<SUB>33</SUB> Alloys

Abstract

Molecular dynamics simulations have been performed to study the dynamical properties of amorphous and liquid Zr67Ni33 alloys. The atomistic vibrational dynamics consist of single-particle motion and cooperative motion. The former is analyzed by the power spectrum of velocity autocorrelation function, the latter by the dynamic structure factor as a function of the wave number. The calculated power spectrum agrees with the previously reported experimental result. The power spectrum of the Zr atom of the amorphous state is similar to that of the crystal state. On the other hand, the power spectrum of Ni shows an obvious difference between amorphous and crystal states. Phonon propagation is observed for the acoustic mode but not for the optical mode. The dispersion relation is observed up to the wave number Q0 where the structure factor shows the first maximum. The acoustic cooperative motion mainly consists of Zr–Zr correlation. On the other hand, no obvious cooperative motion is observed for Ni–Ni correlation. The dynamics of the neighboring atoms are observed by the snapshots of the atom configuration. The model of the dynamical motion of the random-structure Zr–Ni alloy is considered.