Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Abstract

Amorphous solids, such as metallic, polymeric, and colloidal glasses, display complex spatiotemporal response to applied deformations. In contrast to crystalline solids, during loading, amorphous solids exhibit a smooth crossover from elastic response to plastic flow. In this study, we investigate the mechanical response of binary Lennard-Jones glasses to athermal, quasistatic pure shear as a function of the cooling rate used to prepare them. We find several key results concerning the connection between strain-induced particle rearrangements and mechanical response. We show that the energy loss per strain dU loss /dγ caused by particle rearrangements for more rapidly cooled glasses is larger than that for slowly cooled glasses. We also find that the cumulative energy loss U loss can be used to predict the ductility of glasses even in the putative linear regime of stress versus strain. U loss increases (and the ratio of shear to bulk moduli decreases) with increasing cooling rate, indicating enhanced ductility. In addition, we characterized the degree of reversibility of particle motion during a single shear cycle. We find that irreversible particle motion occurs even in the linear regime of stress versus strain. However, slowly cooled glasses, which undergo smaller rearrangements, are more reversible during a single shear cycle than rapidly cooled glasses. Thus, we show that more ductile glasses are also less reversible.

Particle rearrangement and softening contributions to the nonlinear mechanical response of glasses

“…We successively apply affine shear increments δγ followed by potential energy minimization to a total strain γ. Additional details concerning the AQS pure shear algorithm can be found in our previous studies [23].…”

“…In previous simulation studies of AQS pure shear [23], we developed a method to unambiguously determine whether a particle rearrangement event occurs during the strain interval γ to γ+δγ with an accuracy on the order of numerical precision. We denote the total number of rearrangements in the strain interval 0 to γ as N r (γ).…”

“…softening or a decrease in the slopes of stress versus strain) between rearrangements. There have been a number of previous computational studies focusing on either particle rearrangements [12,13,23,50], or softening of the shear modulus [49,51] of binary Lennard Jones glasses under applied deformation. In this article, we will study both and compare the relative contributions from particle rearrangements and softening in determining the ensemble-averaged nonlinear mechanical response of sheared glasses as a function of the cooling rate used to prepare them.…”

“…The cooling rate determines the fictive temperature, at which the system falls out of metastable equilibrium [22]. The fictive temperature significantly affects mechanical properties, such as the ductility [20,[23][24][25][26][27], shear band formation [28], quality factor of vibrations [5], and the relation between stress versus strain under quasistatic compression or tension [29,30].…”

Stable small bubble clusters in two-dimensional foams

“…Stress fluctuations are often characterized by periods of increasing stress followed by sudden decreases, referred to as stress drops [15][16][17][18][19] or avalanches 20 . During flow, particle rearrangements can localize, which gives rise to shear banding [21][22][23][24][25] .…”