在这项工作中，我们研究了电子涡旋在非晶样品中传播时的弹性散射行为。我们使用一个配方的多层方法在圆柱坐标系中，从理论上研究由于散射的强度在不同的角动量分量之间的重新分配。为了证实和阐述我们的理论结果，我们进行了广泛的数值模拟上的三个模型系统（Si $_3$ N $_4$，Fe $_{0.8}$ B $_{0.2}$，Pt）的各种各样的实验参数，以量化的涡流的纯度，净角动量转移，和相对于随机的相对位置之间的结果的变化的电子束和散射原子。这些结果将有助于科学家进一步改进电子涡旋的产生，并增强涉及它们的应用。
英文摘要：
In this work, we study the elastic scattering behavior of electron vortices when propagating through amorphous samples. We use a formulation of the multislice approach in cylindrical coordinates to theoretically investigate the redistribution of intensity between different angular momentum components due to scattering. To corroborate and elaborate on our theoretical results, we perform extensive numerical simulations on three model systems (Si$_3$N$_4$, Fe$_{0.8}$B$_{0.2}$, Pt) for a wide variety of experimental parameters to quantify the purity of the vortices, the net angular momentum transfer, and the variability of the results with respect to the random relative position between the electron beam and the scattering atoms. These results will help scientists to further improve the creation of electron vortices and enhance applications involving them.
We investigate the emergence of isotropic linear elasticity in amorphous and polycrystalline solids, via extensive numerical simulations. We show that the elastic properties are correlated over a finite length scale $ξ_E$, so that the central limit theorem dictates the emergence of continuum linear isotropic elasticity on increasing the specimen size. The stiffness matrix of systems of finite size $L > ξ_E$ is obtained adding to that predicted by linear isotropic elasticity a random one of spectral norm $(L/ξ_E)^{-3/2}$, in three spatial dimensions. We further demonstrate that the elastic leng…
From Amorphous to Amorphous-Crystalline Mixed-Phase Boron Nitride: Evolution of the Thermal and Elastic Properties
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST（加泰罗尼亚纳米科学与纳米技术研究所）；Faculty of Physics, Autonomous University of Barcelona（巴塞罗那自治大学物理系）；Universite Claude Bernard Lyon 1, CNRS, LMI, UMR 5615（里昂第一大学）；Faculty of Physics and Astronomy, Adam Mickiewicz University（亚当密茨凯维奇大学物理与天文学院）；International Iberian Nanotechnology Laboratory（伊比利亚纳米技术国际实验室）；ICREA（加泰罗尼亚高级研究院）
The vibrational density of states $D(ω)$ of solids controls their thermal and transport properties. In crystals, the low-frequency modes are extended phonons distributed in frequency according to Debye's law, $D(ω) \propto ω^2$. In amorphous solids, phonons are damped, and at low frequency $D(ω)$ comprises extended modes in excess over Debye's prediction, leading to the so-called boson peak in $D(ω)/ω^2$ at $ω_{\rm bp}$, and quasi-localized (QLMs) ones. Here we show that boson peak and phonon attenuation in the Rayleigh scattering regime are related, as suggested by correlated fluctuating elas…
Elastic consequences of a single plastic event: towards a realistic account of structural disorder and shear wave propagation in models of flowing amorphous solids
A study of the transverse acoustic phonons on nano-structured AlN films has been carried out by using high-resolution micro-Brillouin spectroscopy. Dense films have been deposited by radio frequency (r.f.) magnetron sputtering under ultra high vacuum at room temperature. Films with different morphologies were prepared and investigated by transmission electron microscopy and Brillouin Spectroscopy (equiaxed nano-sized, nano-columnar grains and amorphous phase). Results show a dependence of the transverse modes on the nano-structure. The nano-columnar film exhibits two transversal modes as expec…
Effects of Cooling Rate on Structural Relaxation in Amorphous Drugs: Elastically Collective Nonlinear Langevin Equation Theory and Machine Learning Study
A theory of vibrational excitations based on power-law spatial correlations in the elastic constants (or equivalently in the internal stress) is derived, in order to determine the vibrational density of states $D(ω)$ of disordered solids. The results provide the first prediction of a boson peak in amorphous materials where spatial correlations in the internal stresses (or elastic constants) are of power-law form, as is often the case in experimental systems, leading to logarithmic enhancement of (Rayleigh) phonon attenuation. A logarithmic correction of the form $\sim -ω^{2}\lnω$ is predicted …
Accurate prediction of structural and mechanical properties on amorphous materials enabled through machine-learning potentials: a case study of silicon nitride
Amorphous solids under mechanical strains are prone to plastic responses. Recent work showed that in amorphous granular system these plastic events, that are typically quadrupolar in nature, can screen the elastic response. When the density of the quadrupoles is high, the gradients of the quadrupole field act as emergent dipole sources, leading to qualitative changes in the mechanical response, as seen for example in the displacement field. In this paper we examine the effect of screening in classical glass formers. These are made of point particles that interact via binary forces. Both invers…
Theoretical model for the structural relaxation time in co-amorphous drugs
我们提出了一个简单的方法来研究非晶药物的结构弛豫时间和玻璃化转变。非晶材料被建模为一组大小相等的硬球。本文用与Kramer理论相联系的Elementary集体非线性Langevin方程理论计算了硬球流体几十年的结构弛豫时间。然后，一个新的热映射从一个真正的材料到一个有效的硬球流体提供了温度依赖的弛豫时间，这可以与实验相比。数值结果定量同意与以前的实验具有不同的重量比的药物二元混合物。我们进行实验，以测试我们的计算依折麦布-辛伐他汀-Kollidon VA 64混合物。我们的方法将提供一个简单而全面的描述非晶复合材料的玻璃态动力学。
Materials with thermal-invariant elastic properties of materials are of interest for resonant device frequency and dimensional stability of precision devices. Here, we demonstrate that the temperature coefficient of elasticity (TCE) of amorphous silica can be locally reduced using femtosecond laser irradiation. Notably, a self-organized laser-induced modification shows a decrease of the TCE beyond 50%. The origin of this dramatic decrease is attributed to the presence of sub-micron permanent densified zones within the fine multi-layers structure of the laser-modified zone.
A new approach is theoretically proposed to study the glass transition of active pharmaceutical ingredients and a glass-forming anisotropic molecular liquid at high pressures. We describe amorphous materials as a fluid of hard spheres. Effects of nearest-neighbor interactions and cooperative motions of particles on glassy dynamics are quantified through a local and collective elastic barrier calculated using the Elastically Collective Nonlinear Langevin Equation theory. Inserting two barriers into Kramer's theory gives structural relaxation time. Then, we formulate a new mapping based on the t…
