# Revisiting the fragile-to-strong crossover in metallic glass-forming liquids: application to Cu$_x$Zr$_x$Al$_{100-2x}$

## TL;DR

This study investigates the fragile-to-strong crossover in metallic glass-forming liquids, specifically Cu-Zr-Al alloys, revealing a lower-than-expected crossover temperature and associated vibrational and viscosity changes through molecular dynamics simulations.

## Contribution

It provides new insights into the temperature at which the fragile-to-strong crossover occurs in Cu-Zr-Al alloys, challenging previous predictions and linking vibrational states to dynamical behavior.

## Key findings

- Crossover temperature is lower than previous predictions.
- Vibrational density of states shows excess low-frequency modes at crossover.
- Shear viscosity exhibits multiple dynamical crossovers near T_g.

## Abstract

The fragile-to-strong crossover seems to be a general feature of metallic glass-forming liquids. Here, we study the behavior of shear viscosity, diffusion coefficient and vibrational density of states for Cu$_\text{x}$Zr$_\text{x}$Al$_{\text{100-2x}}$ alloy through molecular dynamics simulations. The results reveal that the fragile-to-strong temperature (T$_\text{fs}$) and the glass transition temperature (T$_\text{g}$) increase as the aluminum content becomes larger. The inverse of the diffusion coefficient as a function of temperature exhibits a dynamical crossover in the vicinity of T$_\text{g}$, at a much lower temperature than that predicted by nearly all previous studies. At the temperature in which the dynamical crossover occurs determined by the inverse of the diffusion coefficient, we found an excess of vibrational states at low frequencies, resembling a pronounced peak in the reduced vibrational density of states characteristic of a strong liquid. Finally, the behavior of the shear viscosity as a function of reduced temperature (T$_\text{g}$/T) also shows that, besides the fragile-to-strong crossover nearby T$_\text{g}$, another dynamical crossover is present near the onset of the supercooled regime.