We investigate the non-affine displacement fields that occur in two-dimensional Lennard-Jones models of metallic glasses subjected to athermal, quasistatic simple shear (AQS). During AQS, the shear stress versus strain displays continuous quasi-elastic segments punctuated by rapid drops in shear stress, which correspond to atomic rearrangement events. We capture all information concerning the atomic motion during the quasi-elastic segments and shear stress drops by performing Delaunay triangularizations and tracking the deformation gradient tensor F_α associated with each triangle α. To understand the spatio-temporal evolution of the displacement fields during shear stress drops, we calculate F_α along minimal energy paths from the mechanically stable configuration immediately before to that after the stress drop. We find that quadrupolar displacement fields form and dissipate both during the quasi-elastic segments and shear stress drops. We then perform local perturbations (rotation, dilation, simple and pure shear) to single triangles and measure the resulting displacement fields. We find that local pure shear deformations of single triangles give rise to mostly quadrupolar displacement fields, and thus pure shear strain is the primary type of local strain that is activated by bulk, athermal quasistatic simple shear. Other local perturbations, e.g. rotations, dilations, and simple shear of single triangles, give rise to vortex-like and dipolar displacement fields that are not frequently activated by bulk AQS. These results provide fundamental insights into the non-affine atomic motion that occurs in driven, glassy materials.

中文翻译：

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使用 delaunay 三角化来表征非晶固体的非热准静态变形过程中的非仿射位移场

我们研究了在经受非热准静态简单剪切 (AQS) 的金属玻璃的二维 Lennard-Jones 模型中发生的非仿射位移场。在 AQS 期间，剪切应力与应变显示连续的准弹性段，被剪切应力的快速下降打断，这与原子重排事件相对应。我们通过执行 Delaunay 三角化和跟踪与每个三角形α相关联的变形梯度张量F _{α 来}捕获有关准弹性段和剪切应力下降期间原子运动的所有信息。为了理解剪切应力下降过程中位移场的时空演变，我们计算F _α沿着最小的能量路径，从紧接在应力下降之前的机械稳定配置到之后的机械稳定配置。我们发现四极位移场在准弹性段和剪切应力下降期间形成和消散。然后我们对单个三角形执行局部扰动（旋转、膨胀、简单和纯剪切）并测量产生的位移场。我们发现单个三角形的局部纯剪切变形主要产生四极位移场，因此纯剪切应变是由体块非热准静态简单剪切激活的主要局部应变类型。其他局部扰动，例如单个三角形的旋转、膨胀和简单剪切会产生涡状和偶极位移场，这些场不会经常被大量 AQS 激活。这些结果提供了对驱动玻璃材料中发生的非仿射原子运动的基本见解。