Scaling of slip avalanches in sheared amorphous materials based on large-scale atomistic simulations

摘要

Atomistic simulations of binary amorphous systems with over 4 million atoms are performed. Systems oftwo interatomic potentials of the Lennard-Jones type, LJ12-6 and LJ9-6, are simulated. The athermal quasistaticshearing protocol is adopted, where the shear strain is applied in a stepwise fashion with each step followed byenergy minimization. For each avalanche event, the shear stress drop (σ), the hydrostatic pressure drop (σh),and the potential energy drop (△E) are computed. It is found that, with the avalanche size increasing, the threebecome proportional to each other asymptotically. The probability distributions of avalanche sizes are obtainedand values of scaling exponents fitted. In particular, the distributions follow a power law, P(△U) ～ △U~(−τ) ,where △U is a measure of avalanche sizes defined based on shear stress drops. The exponent τ is 1.25 ± 0.1 forthe LJ12-6 systems, and 1.15 ± 0.1 for the LJ9-6 systems. The value of τ for the LJ12-6 systems is consistentwith that from an earlier atomistic simulation study by Robbins et al. [Phys. Rev. Lett. 109, 105703 (2012)], butthe fitted values of other scaling exponents differ, which may be because the shearing protocol used here differsfrom that in their study.