Transient Nature of the Relaxation Process with Very Short Relaxation Times in Cu–Zr Metallic Glass: Comparison of MACE and EAM in MD-DMS Modeling

The fast mechanical response of Cu64Zr36 metallic glass at 300 K is studied using molecular-dynamics dynamical mechanical spectroscopy (MD-DMS). A validated DFT-trained MACE potential is compared with a classical EAM potential under the same oscillatory shear protocol. For each potential, five independent glass realizations are examined at periods of 20 and 50 ps (50 and 20 GHz, respectively) and a strain amplitude of 1%. Positive G'' and tan δ are obtained in all 20 simulations. For MACE, the mean G'' values ± sample standard deviation are 1.30 ± 0.40 and 1.33 ± 0.42 GPa at periods of 20 and 50 ps; the corresponding EAM values are 1.75 ± 0.60 and 1.55 ± 0.20 GPa. Mean G ' values lie between 17.49 and 18.49 GPa. Quantitative D_min² analysis gives an active-atom fraction of 3.39–3.42% for MACE and 2.18–2.32% for EAM using the threshold D_min² > 8 Å2. About 80% of the active atoms are Cu, whereas the overall atomic Cu fraction in the glass is 64%. The cycle-wise relation between G '' and the active-atom fraction depends on the realization and period and is not one-to-one. The results show that a fast dissipative component persists after replacing EAM with MACE within the investigated frequency window. They do not, however, establish a fully frequency-independent NCL plateau.