Steady shear flows of dense athermal systems composed of soft disks are investigated via non-equilibrium molecular dynamics simulations, from which we sort out links among the structure, dynamics, and shear rheology. ...Steady shear flows of dense athermal systems composed of soft disks are investigated via non-equilibrium molecular dynamics simulations, from which we sort out links among the structure, dynamics, and shear rheology. The systems at rest are jammed packings of frictionless disks with a nonzero yield stress. Driven by low shear rates, the flows shear thin due to the presence of the nonzero yield stress, but transit to shear thickening above a crossover shear rate γc - At γc, we observe the strongest struc- tural anisotropy in the pair distribution function, which serves as the structural signature of the shear thinning-thickening tran- sition. We also observe dynamical signatures associated with the transition： At γc , scaling behaviors of both the mean squared displacement and relaxation time undergo apparent changes. By performing a simple energy analysis, we reveal an underlying condition for the shear thickening to occur： d（lnTg）/d（Inγ） 〉 2 with Tg the kinetic temperature. This condition is confirmed by simulations.展开更多
基金supported by the National Natural Science Foundation of China(21325418,11074228)the National Basic Research Program of China(2012CB821500)+1 种基金the CAS 100-Talent Program(2030020004)the Fundamental Research Funds for the Central Universities(2340000034,2340000060,2030020023)
文摘Steady shear flows of dense athermal systems composed of soft disks are investigated via non-equilibrium molecular dynamics simulations, from which we sort out links among the structure, dynamics, and shear rheology. The systems at rest are jammed packings of frictionless disks with a nonzero yield stress. Driven by low shear rates, the flows shear thin due to the presence of the nonzero yield stress, but transit to shear thickening above a crossover shear rate γc - At γc, we observe the strongest struc- tural anisotropy in the pair distribution function, which serves as the structural signature of the shear thinning-thickening tran- sition. We also observe dynamical signatures associated with the transition： At γc , scaling behaviors of both the mean squared displacement and relaxation time undergo apparent changes. By performing a simple energy analysis, we reveal an underlying condition for the shear thickening to occur： d（lnTg）/d（Inγ） 〉 2 with Tg the kinetic temperature. This condition is confirmed by simulations.
