Diffusion of tracer particles in active bath has attracted extensive attention in recent years.So far,most studies have considered isotropic spherical tracer particles,while the diffusion of anisotropic particles has ...Diffusion of tracer particles in active bath has attracted extensive attention in recent years.So far,most studies have considered isotropic spherical tracer particles,while the diffusion of anisotropic particles has rarely been involved.Here we investigate the diffusion dynamics of a rigid rod tracer in a bath of active particles by using Langevin dynamics simulations in a two-dimensional space.Particular attention is paid to how the translation(rotation)diffusion coefficient D_(T)(D_(R))change with the length of rod L and active strength Fa.In all cases,we find that rod exhibits superdiffusion behavior in a short time scale and returns to normal diffusion in the long time limit.Both D_(T) and D_(R) increase with Fa,but interestingly,a nonmonotonic dependence of D_(T)(D_(R))on the rod length has been observed.We have also studied the translation-rotation coupling of rod,and interestingly,a negative translation-rotation coupling is observed,indicating that rod diffuses more slowly in the parallel direction compared to that in the perpendicular direction,a counterintuitive phenomenon that would not exist in an equilibrium counterpart system.Moreover,this anomalous(diffusion)behavior is reentrant with the increase of Fa,suggesting two competitive roles played by the active feature of bath particles.展开更多
Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact ...Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact on the mechanical response of metallic glasses remain a puzzle.In this work,the plastic flow of the Zr35Ti30Cu8.25Be26.75 metallic glass with the applied ultrasonic-vibration energy of 140 J was investigated by nanoindentation.Both Kelvin and Maxwell-Voigt models have been adopted to analyze the structural evolution during the creep deformation.The increase of the characteristic relaxation time and the peak intensity of relaxation spectra can be found in the sample after ultrasonic vibration.It effectively improves the activation energy of atomic diffusion during the glass transition(Eg)and the growth of the crystal nucleus(Ep).A more homogenous plastic deformation with a weak loading-rate sensitivity of stress exponent is observed in the ultrasonic-vibrated sample,which coincides with the low pile-up and penetration depth as shown in the cross profile of indents.The structural rearrangement under resonance actuation demonstrated in this work might help us better understand the defect-activation mechanism for the plastic flow of amorphous systems.展开更多
基金supported by the Ministry of Science and Technology of China(2016YFA0400904 and 2018YFA0208702)the National Natural Science Foundation of China(No.21973085,No.21833007,No.21790350,No.21673212,No.21521001 and No.21473165)+1 种基金the Fundamental Research Funds for the Central Universities(WK2340000074)Anhui Initiative in Quantum Information Technologies(AHY090200)。
文摘Diffusion of tracer particles in active bath has attracted extensive attention in recent years.So far,most studies have considered isotropic spherical tracer particles,while the diffusion of anisotropic particles has rarely been involved.Here we investigate the diffusion dynamics of a rigid rod tracer in a bath of active particles by using Langevin dynamics simulations in a two-dimensional space.Particular attention is paid to how the translation(rotation)diffusion coefficient D_(T)(D_(R))change with the length of rod L and active strength Fa.In all cases,we find that rod exhibits superdiffusion behavior in a short time scale and returns to normal diffusion in the long time limit.Both D_(T) and D_(R) increase with Fa,but interestingly,a nonmonotonic dependence of D_(T)(D_(R))on the rod length has been observed.We have also studied the translation-rotation coupling of rod,and interestingly,a negative translation-rotation coupling is observed,indicating that rod diffuses more slowly in the parallel direction compared to that in the perpendicular direction,a counterintuitive phenomenon that would not exist in an equilibrium counterpart system.Moreover,this anomalous(diffusion)behavior is reentrant with the increase of Fa,suggesting two competitive roles played by the active feature of bath particles.
基金the National Natural Science Foundation of China(51631003,51871157 and 51601038)the Key Basic and Applied Research Program of Guangdong Province,China(2019B030302010)+3 种基金the Natural Science Foundation of Jiangsu Province,China(BK20171354)the Fundamental Research Funds for the Central Universities(2242020K40002)the Research and Practice Innovation Program for Postgraduates in Jiangsu Province(SJCX20_0038)Jiangsu Key Laboratory for Advanced Metallic Materials(BM2007204)。
文摘Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact on the mechanical response of metallic glasses remain a puzzle.In this work,the plastic flow of the Zr35Ti30Cu8.25Be26.75 metallic glass with the applied ultrasonic-vibration energy of 140 J was investigated by nanoindentation.Both Kelvin and Maxwell-Voigt models have been adopted to analyze the structural evolution during the creep deformation.The increase of the characteristic relaxation time and the peak intensity of relaxation spectra can be found in the sample after ultrasonic vibration.It effectively improves the activation energy of atomic diffusion during the glass transition(Eg)and the growth of the crystal nucleus(Ep).A more homogenous plastic deformation with a weak loading-rate sensitivity of stress exponent is observed in the ultrasonic-vibrated sample,which coincides with the low pile-up and penetration depth as shown in the cross profile of indents.The structural rearrangement under resonance actuation demonstrated in this work might help us better understand the defect-activation mechanism for the plastic flow of amorphous systems.
