Wu Bin, Iwashita Takuya, Egami Takeshi
Department of Physics and Astronomy, Joint Institute of Neutron Science, University of Tennessee, Knoxville, Tennessee 37996, USA.
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Mar;91(3):032301. doi: 10.1103/PhysRevE.91.032301. Epub 2015 Mar 2.
In this paper we demonstrate the presence of anisotropic stress correlations in the simulated two-dimensional liquids. Whereas the temporal correlation of macroscopic shear stress is known to contribute to viscosity via the Green-Kubo formula, the general question regarding angular dependence of the spatial correlation among atomic-level stresses in liquids without external shear has not been explored. We observed the apparent anisotropicity with well-defined symmetry which can be explained in terms of the elastic continuum theory by Eshelby. In addition, we found that the shear stress correlation is screened compared to the prediction by the elastic continuum theory, and the screening length depends on temperature and follows the power law, suggesting divergence around the glass transition temperature. The success of the Eshelby theory to explain the anisotropy of the stress correlations justifies the idea that the mismatch between the atom and its nearest neighbor cage produces the atomic-level stress as well as the long-range stress fields.
在本文中，我们证明了在模拟的二维液体中存在各向异性应力相关性。虽然宏观剪切应力的时间相关性已知通过格林-库博公式对粘度有贡献，但关于无外部剪切的液体中原子级应力之间空间相关性的角度依赖性这一普遍问题尚未得到探索。我们观察到具有明确对称性的明显各向异性，这可以用埃舍尔比的弹性连续介质理论来解释。此外，我们发现与弹性连续介质理论的预测相比，剪切应力相关性受到了屏蔽，并且屏蔽长度取决于温度并遵循幂律，表明在玻璃化转变温度附近发散。埃舍尔比理论成功地解释了应力相关性的各向异性，这证明了原子与其最近邻笼之间的不匹配会产生原子级应力以及长程应力场这一观点的合理性。
