Nonaffine rearrangements of atoms in deformed and quiescent binary glasses

The influence of periodic shear deformation on nonaffine atomic displacements in an amorphous solid is examined via molecular dynamics simulations. We study the three-dimensional Kob-Andersen binary mixture model at a finite temperature. It is found that when the material is periodically strained, most of the atoms undergo repetitive nonaffine displacements with amplitudes that are broadly distributed. We show that particles with large amplitudes of nonaffine displacements are organized into compact clusters. With increasing strain amplitude, spatial correlations of nonaffine displacements become increasingly long-ranged, although they remain present even in a quiescent system due to thermal fluctuations.

Figure 1

The instantaneous atomic positions for a binary LJ glass annealed with a slow cooling rate of ${10}^{-5}\varepsilon /k_B\tau$ to the temperature $T_{\text{LJ}}={10}^{-2}\varepsilon /k_B$. Atoms of type A are shown by large blue circles, and those of type B by small red circles. The arrows indicate the plane of periodic shear deformation.

Figure 2

The potential energy per atom $U$ (in units of $\varepsilon$) during ten oscillation cycles for the strain amplitudes ${\gamma }_0=0$, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08 (from bottom to top).

Figure 3

The probability distribution function of $D^2(t,T/4)$ for the strain amplitudes ${\gamma }_0=0$, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08 (from left to right). The straight solid line indicates the slope $-2$.

Figure 4

Variation of the averaged quantity $D^2(t,\mathrm{\Delta }t)$ during one oscillation period for the strain amplitudes ${\gamma }_0=0$, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08 (from bottom to top).

Figure 5

Spatial configurations of atoms with large nonaffine displacements after a quarter of a cycle, $D^2(t,T/4)>0.01{\sigma }^2$, for the strain amplitudes (a) ${\gamma }_0=0.00$, (b) ${\gamma }_0=0.02$, (c) ${\gamma }_0=0.04$, and (d) ${\gamma }_0=0.06$. The atoms of type A and B are denoted by blue and red circles, respectively.

Figure 6

The correlation function $C_{D^2}\left(\mathrm{\Delta }\mathbf{r}\right)$ defined by Eq. (4) for the strain amplitudes ${\gamma }_0=0$, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08 (from left to right). The straight line with the slope $-2$ is plotted for reference. The inset shows the same data on the log-normal scale.