软凝聚态物理
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- [1] arXiv:2507.12597 [中文pdf, pdf, html, 其他]
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标题： 二维$p$-atics 中通过周期边界缺陷相互作用标题： Defect Interactions Through Periodic Boundaries in Two-Dimensional $p$-atics评论： 7 + 16页，4 + 4图主题： 软凝聚态物理 (cond-mat.soft)
周期性边界条件是一种常用的工具，用于有效地模拟无限域。 然而，二维周期性域在拓扑上与无限平面不同，这引发了这样一个问题：周期性边界条件如何影响本身具有拓扑性质的系统？ 在本工作中， 我推导出二维$p$-atic液晶的取向场的解析表达式，这些系统具有$p$-重旋转对称性，在受二维周期性边界条件约束的平面上存在拓扑缺陷。 我展示了这种取向场会导致缺陷之间出现异常的相互作用，这种相互作用偏离了通常的库仑相互作用，这一结论通过向列液晶（$p = 2$）的连续体模拟得到了验证。 这种相互作用被理解为由指向场中的非奇异拓扑孤子介导的，这些孤子由周期性边界条件稳定。 结果表明，在分析拓扑缺陷之间的相互作用时，考虑域的拓扑结构而不是仅仅几何结构是重要的。
Periodic boundary conditions are a common tool used to emulate effectively infinite domains. However, two-dimensional periodic domains are topologically distinct from the infinite plane, eliciting the question: How do periodic boundaries affect systems with topological properties themselves? In this work, I derive an analytical expression for the orientation fields of two-dimensional $p$-atic liquid crystals, systems with $p$-fold rotational symmetry, with topological defects in a flat domain subject to periodic boundary conditions in two-dimensions. I show that this orientation field leads to an anomalous interaction between defects that deviates from the usual Coulomb interaction, which is confirmed through continuum simulations of nematic liquid crystals ($p = 2$). The interaction is understood as being mediated by non-singular topological solitons in the director field which are stabilized by the periodic boundary conditions. The results show the importance of considering domain topology, not only geometry, when analyzing interactions between topological defects.
- [2] arXiv:2507.12683 [中文pdf, pdf, 其他]
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标题： 基于物理信息的数据驱动方法用于多轴循环载荷下可压缩非线性历史依赖软材料的本构建模发现标题： A Physics-Informed Data-Driven Discovery for Constitutive Modeling of Compressible, Nonlinear, History-Dependent Soft Materials under Multiaxial Cyclic Loading主题： 软凝聚态物理 (cond-mat.soft)
我们提出了一种通用的混合物理信息机器学习框架，用于建模多轴循环载荷下的非线性、历史依赖的粘弹性行为。 该方法基于一种基于广义内部状态变量的粘-超弹性本构公式，其中应力被分解为体积部分、等容超弹性部分和等容粘弹性部分。 高斯过程回归（GPR）对平衡响应进行建模，而具有长短期记忆（LSTM）单元的循环神经网络（RNN）捕捉时间依赖的粘弹性效应。 物理约束，包括客观性、材料对称性和热力学一致性，被施加以确保物理有效的预测。 在开发基于张量完整性基和响应函数的代理模型的一般形式后，我们采用了非线性Holzapfel微分粘弹性模型来生成训练数据。 构建了两个数据集，一个用于短期松弛，另一个用于长期松弛，以涵盖广泛的材料记忆特性。 该模型在多种多轴加载条件下进行训练和测试，包括在纵向和横向方向上独立施加的不同拉伸水平、变化的应变率以及拉伸和压缩状态，甚至超出训练域。 对两个数据集在不同应变率下的能量耗散进行了显式分析，通过第二定律验证热力学一致性。 结果表明，所提出的框架能够准确捕捉复杂的、非线性且与速率相关的材料响应。 此外，它对合成噪声表现出强大的鲁棒性，使得在现实和可变加载场景下能够进行可推广且物理一致的预测。
We propose a general hybrid physics-informed machine learning framework for modeling nonlinear, history-dependent viscoelastic behavior under multiaxial cyclic loading. The approach is built on a generalized internal state variable-based visco-hyperelastic constitutive formulation, where stress is decomposed into volumetric, isochoric hyperelastic, and isochoric viscoelastic components. Gaussian Process Regression (GPR) models the equilibrium response, while Recurrent Neural Networks (RNNs) with Long Short-Term Memory (LSTM) units capture time-dependent viscoelastic effects. Physical constraints, including objectivity, material symmetry, and thermodynamic consistency, are enforced to ensure physically valid predictions. After developing the general form of the surrogate model based on tensor integrity bases and response functions, we employed the nonlinear Holzapfel differential viscoelastic model to generate training data. Two datasets, one for short-term and another for long-term relaxation, are constructed to span a wide range of material memory characteristics. The model is trained and tested under diverse multiaxial loading conditions, including different stretch levels applied independently in the longitudinal and transverse directions, varying strain rates, and both tension and compression states, even beyond the training domain. Energy dissipation is explicitly analyzed at different strain rates for both datasets to verify thermodynamic consistency through the second law. The results show that the proposed framework accurately captures complex, nonlinear, and rate-dependent material responses. Moreover, it demonstrates strong robustness to synthetic noise, enabling generalizable and physically consistent predictions under realistic and variable loading scenarios.
- [3] arXiv:2507.12694 [中文pdf, pdf, 其他]
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标题： 强非线性粘弹性软材料中的应力软化损伤 带有时温耦合的物理信息数据驱动本构模型标题： Stress Softening Damage in Strongly Nonlinear Viscoelastic Soft Materials A Physics Informed Data Driven Constitutive Model with Time Temperature Coupling主题： 软凝聚态物理 (cond-mat.soft)
本研究提出了一种新颖的物理信息数据驱动建模框架，用于捕捉表现出应力软化的软材料的强非线性热粘弹性行为，重点在于穆林斯效应。 与以往仅限于准静态或等温条件的方法不同，我们的模型统一了速率依赖性、温度敏感性、大应变循环加载和演变损伤机制。 通过自定义损失函数确保热力学可行性，该函数嵌入了克劳修斯-杜赫姆不等式，并显式约束损伤变量以实现物理上现实的软化。 时间卷积网络在多个温度、应变率和拉伸水平的高保真实验数据上进行训练，使模型能够捕捉丰富的热机械耦合和历史依赖性。 该框架可推广到未见过的热机械条件、更高的应变率和更大的变形，并对输入噪声具有鲁棒性。 与使用Abaqus/Explicit的有限元模拟对比验证表明，在循环加载和损伤演化下具有良好的一致性，证实了代理模型在高级仿真工作流中的有效性。
This study presents a novel physics informed, data-driven modeling framework for capturing the strongly nonlinear thermo-viscoelastic behavior of soft materials exhibiting stress softening, with emphasis on the Mullins effect. Unlike previous approaches limited to quasi-static or isothermal conditions, our model unifies rate dependence, temperature sensitivity, large strain cyclic loading, and evolving damage mechanisms. Thermodynamic admissibility is ensured via a custom loss function that embeds the Clausius Duhem inequality and explicitly constrains the damage variable for physically realistic softening. A Temporal Convolutional Network is trained on high fidelity experimental data across multiple temperatures, strain rates, and stretch levels, enabling the model to capture rich thermomechanical coupling and history dependence. The framework generalizes to unseen thermo mechanical conditions, higher strain rates, and larger deformations, and remains robust to input noise. Validation against finite element simulations using Abaqus/Explicit demonstrates excellent agreement under cyclic loading and damage evolution, confirming the surrogate models effectiveness for advanced simulation workflows.
- [4] arXiv:2507.12738 [中文pdf, pdf, html, 其他]
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标题： 紧邻堆积转变附近的广范围双分散性下的超均匀性标题： Hyperuniformity near jamming transition over a wide range of bidispersity评论： 11页，9图主题： 软凝聚态物理 (cond-mat.soft)
我们数值研究了二维无摩擦的双分散系统紧密堆积中的超均匀性。 超均匀性通过大尺度上的密度涨落抑制来表征，在小波数极限下结构因子渐近趋于零，如$S(q) \propto q^{\alpha}$所示，其中$\alpha > 0$。 众所周知，紧密排列配置在广泛的波数窗口内表现出超均匀性，直至$q^{\ast}\sigma \approx 0.2$，其中$\sigma$是粒子直径。 在二维情况下，我们发现指数$\alpha$大约为$0.6\text{--}0.7$。 这与三维系统报告的$\alpha = 1$值形成对比。 我们采用Rissone \textit{等.} \href{https://link.aps.org/doi/10.1103/PhysRevLett.127.038001}{[物理评论快报{\bf 127}，038001 (2021)]}最近引入的一种先进方法，最初用于单分散和三维系统，以高精度确定 $\alpha$。 该指数在所有小颗粒和大颗粒之间的尺寸比下保持不变，除了在单分散情况下，系统会结晶。
We numerically investigate hyperuniformity in two-dimensional frictionless jammed packings of bidisperse systems. Hyperuniformity is characterized by the suppression of density fluctuations at large length scales, and the structure factor asymptotically vanishes in the small-wavenumber limit as $S(q) \propto q^{\alpha}$, where $\alpha > 0$. It is well known that jammed configurations exhibit hyperuniformity over a wide range of wavenumbers windows, down to $q^{\ast}\sigma \approx 0.2$, where $\sigma$ is the particle diameter. In two dimensions, we find that the exponent $\alpha$ is approximately $0.6\text{--}0.7$. This contrasts with the reported value of $\alpha = 1$ for three-dimensional systems. We employ an advanced method recently introduced by Rissone \textit{et al.} \href{https://link.aps.org/doi/10.1103/PhysRevLett.127.038001}{[Phys. Rev. Lett. {\bf 127}, 038001 (2021)]}, originally developed for monodisperse and three-dimensional systems, to determine $\alpha$ with high precision. This exponent is found to be unchanged for all size ratios between small and large particles, except in the monodisperse case, where the system crystallizes.
- [5] arXiv:2507.12811 [中文pdf, pdf, html, 其他]
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标题： 手性活性浴中对称包含物的自发旋转标题： Spontaneous Rotation of a Symmetric Inclusion in Chiral Active Bath评论： 共有9页和7图主题： 软凝聚态物理 (cond-mat.soft)
我们研究了一个称为扭矩器的圆形被动包含物在手性活性布朗粒子浴中的动力学。尽管几何对称且不具有运动能力，但由于与活性粒子的角向偏置碰撞产生的空间非均匀扭矩，扭矩器表现出持续旋转。这种由相互作用驱动的对称性破缺并不依赖于形状各向异性或外部施力。通过模拟，我们识别出两种不同的旋转模式：一种在低手性下由密度梯度主导，另一种在高手性下由增加的碰撞频率主导。我们的结果突显了手性活性介质中的非平衡相互作用如何在对称物体中引发运动，为活性系统中的对称性破缺提供了新的视角。
We study the dynamics of a circular passive inclusion, termed a torquer, in a bath of chiral active Brownian particles. Despite being geometrically symmetric and non-motile, the torquer exhibits persistent rotation due to spatially inhomogeneous torques arising from angularly biased collisions with active particles. This interaction-driven symmetry breaking does not rely on shape anisotropy or external forcing. Through simulations, we identify two distinct regimes of rotation: one dominated by density gradients at low chirality, and another by increased impact frequency at high chirality. Our results highlight how nonequilibrium interactions in chiral active media can induce motion in symmetric objects, offering a new perspective on symmetry breaking in active systems.
- [6] arXiv:2507.12895 [中文pdf, pdf, html, 其他]
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标题： 驱动多稳态材料中的条带形成和极化标题： Banding and polarization in driven multistable materials主题： 软凝聚态物理 (cond-mat.soft) ; 无序系统与神经网络 (cond-mat.dis-nn)
我们研究了一个受周期应变作用的双稳态键的无序网络。 该模型受到对皱褶纸张实验的启发，其特征行为与玻璃相关，包括复杂的能量景观、记忆效应和大的雪崩现象。 在小应变幅度下，系统迅速收敛到一个极限环，其中系统在一组状态之间反复循环。 在大振幅下，运动是混乱的，并不收敛到极限环。 过渡似乎具有连续性，时间尺度趋于发散。 过渡两侧的不稳定性质不同。 在小应变幅度下，不稳定仅在有限距离内相关。 在转换之上，不稳定沿对角带局部化。 带之间的距离在接近转换时增长并似乎发散。 我们提出一个简单的模型来解释这些观察结果。 在转换之下，我们提出一个新的“序参数”——沿驱动方向的不稳定性的极化。
We study a disordered network of bistable bonds subjected to periodic strain. The model is inspired by experiments on crumpled sheets and it features behaviors associated with glasses, including a complex energy landscape, memories, and large avalanches. At small strain amplitudes, the system quickly converges to a limit cycle where the system repeatedly cycles between a set of states. At large amplitudes, motion is erratic and does not converge to a limit cycle. The transition appears to be continuous, with diverging time scales. The nature of instabilities is different on both sides of the transition. At small strain amplitudes, instabilities are correlated only over a finite distance. Above the transition, instabilities are localized along diagonal bands. The distance between bands grows near the transition and appears to diverge. We propose a simple model that explains these observations. Below the transition, we propose a new ``order parameter'' -- the polarization of the instabilities along the driving direction.
- [7] arXiv:2507.12934 [中文pdf, pdf, html, 其他]
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标题： 机器学习带电胶体在原始1:1电解质中的多体势能标题： Machine learning many-body potentials for charged colloids in primitive 1:1 electrolytes评论： 13页，7图主题： 软凝聚态物理 (cond-mat.soft)
带电粒子在电解质中的有效相互作用最常使用Derjaguin-Landau-Verwey-Overbeek(DLVO)势来建模，在该模型中，悬浮液中的离子在平均场层面上被粗粒化处理。 然而，一些实验表明该理论存在不足，因为在强库仑耦合区域（例如低温度、低介电常数、高离子价态、高表面电荷）中，围绕胶体的离子分布由非平凡的相关性所支配。 通过在这些胶体悬浮液的模拟中显式包含离子可以获得见解，尽管直接模拟高度带电球体的分散体系在计算上是具有挑战性的。 为了克服缓慢的平衡问题，我们采用机器学习(ML)框架生成准确描述有效胶体相互作用的ML势。 这些ML势使得快速模拟成为可能，并使得在悬浮液中对带电胶体的大规模模拟成为可能，从而为系统研究它们的相行为（特别是气液和流固共存）提供了可能性。
Effective interactions between charged particles dispersed in an electrolyte are most commonly modeled using the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential, where the ions in the suspension are coarse-grained out at mean-field level. However, several experiments point to shortcomings of this theory, as the distribution of ions surrounding colloids is governed by nontrivial correlations in regimes of strong Coulomb coupling (e.g. low temperature, low dielectric constant, high ion valency, high surface charge). Insight can be gained by explicitly including the ions in simulations of these colloidal suspensions, even though direct simulations of dispersions of highly charged spheres are computationally demanding. To circumvent slow equilibration, we employ a machine-learning (ML) framework to generate ML potentials that accurately describe the effective colloid interactions. These ML potentials enable fast simulations and make large-scale simulations of charged colloids in suspension possible, opening the possibility for a systematic study of their phase behaviour, in particular gas-liquid and fluid-solid coexistence.
- [8] arXiv:2507.13166 [中文pdf, pdf, html, 其他]
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标题： 设计具有简单相互作用的胶体粒子二元混合物以组装复杂晶体标题： Designing binary mixtures of colloidal particles with simple interactions that assemble complex crystals主题： 软凝聚态物理 (cond-mat.soft)
用于设计胶体粒子之间相互作用以诱导自组装的计算方法因其有望发现定制材料而受到广泛关注。 然而，将计算设计的相互作用转化为实验仍然常常是一个挑战，因为它们可能具有过于复杂甚至无法物理实现的特性。 为了弥合这一差距，我们利用相对熵最小化来设计能够组装晶体超晶格的二元胶体粒子对势。 我们通过施加由DNA功能化纳米颗粒所激发的物理动机的对势形式和参数化的约束，降低了相互作用设计空间的维度和范围。 我们表明，即使结构复杂，诸如蜂窝状和立方钻石等二维和三维晶格也可以使用简单的相互作用进行组装。 我们还发现，设计参数所使用的初始条件以及组装协议在决定组装过程的结果和成功方面起着重要作用。
Computational methods for designing interactions between colloidal particles that induce self-assembly have received much attention for their promise to discover tailored materials. However, it often remains a challenge to translate computationally designed interactions to experiments because they may have features that are too complex, or even infeasible, to physically realize. Toward bridging this gap, we leverage relative-entropy minimization to design pair potentials for binary mixtures of colloidal particles that assemble crystal superlattices. We reduce the dimensionality and extent of the interaction design space by enforcing constraints on the form and parametrization of the pair potentials that are physically motivated by DNA-functionalized nanoparticles. We show that several two- and three-dimensional lattices, including honeycomb and cubic diamond, can be assembled using simple interactions despite their complex structures. We also find that the initial conditions used for the designed parameters as well as the assembly protocol play important roles in determining the outcome and success of the assembly process.
- [9] arXiv:2507.13258 [中文pdf, pdf, html, 其他]
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标题： 粒子尺寸多分散性对薄膜胶体晶体质量的影响标题： Impact of particle-size polydispersity on the quality of thin-film colloidal crystals评论： 10页，5图主题： 软凝聚态物理 (cond-mat.soft)
胶体粒子的尺寸多分散性会破坏其自组装中的秩序，最终导致结晶的完全抑制。 与各种计算研究相反，很少有实验研究系统地探讨尺寸多分散性对胶体晶体质量的影响。 我们进行了一项实验研究，研究从具有系统变化的多分散性的胶体分散液垂直干燥形成的薄层晶体中的结构秩序。 如预期的那样，多分散性的增加会导致秩序恶化，在8%和12%多分散性时局部键取向秩序出现显著下降。 我们的结果与之前提出的在对流组装过程中二维层的外延类似生长模型一致。 我们的结果可以为从更多多分散的系统（如通过更可持续的方法合成的系统）实现胶体晶体的允许极限提供关键见解。
Size polydispersity in colloidal particles can disrupt order in their self-assembly, ultimately leading to a complete suppression of crystallization. In contrast to various computational studies, few experimental studies systematically address the effects of size polydispersity on the quality of colloidal crystals. We present an experimental study of structural order in thin films of crystals vertically dried from colloidal dispersions with a systematically varying polydispersity. As expected, an increase in polydispersity leads to a deterioration in order with significant drops in the local bond-orientational order at 8% and 12% polydispersity. Our results align with previously suggested models of epitaxial-like growth of 2D layers during convective assembly. Our results can offer critical insights into the permissible limits for achieving colloidal crystals from more polydisperse systems such as those synthesized through more sustainable methods.
新提交 (展示 9 之 9 条目 )
- [10] arXiv:2507.12610 (交叉列表自 physics.comp-ph) [中文pdf, pdf, html, 其他]
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标题： TinyDEM：具有滑动、滚动和扭转摩擦的最小开放颗粒DEM代码标题： TinyDEM: Minimal open granular DEM code with sliding, rolling and twisting friction评论： 14页，6图，3表主题： 计算物理 (physics.comp-ph) ; 软凝聚态物理 (cond-mat.soft)
本文介绍了TinyDEM，这是一个在3D中实现的轻量级完整离散元方法（DEM）求解器。 显式求解牛顿阻尼运动方程，用于多分散的干燥、柔软、颗粒状球形粒子的平移和旋转，使用四元数表示其空间方向，避免万向节锁。 粒子碰撞被建模为非弹性和有摩擦的，包括扭矩的完全交换。 通过通用的粒子-网格碰撞例程，可以模拟复杂的刚性几何结构。 TinyDEM设计为一个紧凑的独立程序，使用简单的C++11编写，不包含显式的指针算术和高级概念，如手动内存管理或多态性。 它使用OpenMP进行并行化，并在3条款BSD许可证下免费发布。 TinyDEM可以作为进入经典DEM模拟的入门点，或者作为粒子动力学更复杂模型的基础。
This article introduces TinyDEM, a lightweight implementation of a full-fledged discrete element method (DEM) solver in 3D. Newton's damped equations of motion are solved explicitly for translations and rotations of a polydisperse ensemble of dry, soft, granular spherical particles, using quaternions to represent their orientation in space without gimbal lock. Particle collisions are modeled as inelastic and frictional, including full exchange of torque. With a general particle-mesh collision routine, complex rigid geometries can be simulated. TinyDEM is designed to be a compact standalone program written in simple C++11, devoid of explicit pointer arithmetics and advanced concepts such as manual memory management or polymorphism. It is parallelized with OpenMP and published freely under the 3-clause BSD license. TinyDEM can serve as an entry point into classical DEM simulations or as a foundation for more complex models of particle dynamics.
交叉提交 (展示 1 之 1 条目 )
- [11] arXiv:2503.02806 (替换) [中文pdf, pdf, html, 其他]
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标题： 基于振动模态的非仿射理论预测聚合物熔体的粘度标题： Viscosity of polymer melts using non-affine theory based on vibrational modes期刊参考： 化学物理杂志 162，244504 (2025)主题： 软凝聚态物理 (cond-mat.soft) ; 无序系统与神经网络 (cond-mat.dis-nn) ; 材料科学 (cond-mat.mtrl-sci) ; 统计力学 (cond-mat.stat-mech) ; 化学物理 (physics.chem-ph)
粘度是液体的基本传输和流变性质，它量化了分子层之间相对运动的阻力，并在理解材料行为中起着关键作用。 传统方法，如Green-Kubo（GK）方法，依赖于关联函数的时间积分，由于玻璃转变附近相关性衰减缓慢，计算量变得非常大。 一种基于非仿射晶格动力学（NALD）和瞬时正常模分析的新方法为估算粘度提供了一个有希望的替代方案。 在本研究中，我们将NALD方法应用于Kremer-Grest聚合物系统，在不同温度下计算粘度，并将这些结果与GK方法和非平衡分子动力学模拟的结果进行比较。 我们的研究发现，所有振动模式，包括瞬时正常模，都对粘度有贡献。 这项工作提出了一个高效的框架，用于计算各种系统中的粘度，包括玻璃转变附近，此时GK方法已不再适用。 此外，它为理解与结构相关的不同振动模式的作用开辟了途径，有助于设计具有可调流变性能的材料。
Viscosity, a fundamental transport and rheological property of liquids, quantifies the resistance to relative motion between molecular layers and plays a critical role in understanding material behavior. Conventional methods, such as the Green-Kubo (GK) approach, rely on time integration of correlation functions, which becomes computationally intensive near the glass transition due to slow correlation decay. A recently proposed method based on non-affine lattice dynamics (NALD) and instantaneous normal mode analysis offers a promising alternative for estimating the viscosity. In this study, we apply the NALD approach to compute the viscosity of the Kremer-Grest polymer system over a range of temperatures and compare these results with those from the GK method and non-equilibrium molecular dynamics simulations. Our findings reveal that all vibration modes, including the instantaneous normal modes, contribute to the viscosity. This work presents an efficient framework for calculating viscosity across diverse systems, including near the glass transition where the GK method is no longer applicable. Also, it opens the avenue to understanding the role of different vibrational modes linked with structure, facilitating the design of materials with tunable rheological properties.
- [12] arXiv:2507.09250 (替换) [中文pdf, pdf, html, 其他]
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标题： 二维非晶固体中剪切带的微观起源来自拓扑缺陷标题： Microscopic origin of shear bands in 2D amorphous solids from topological defects主题： 软凝聚态物理 (cond-mat.soft) ; 无序系统与神经网络 (cond-mat.dis-nn) ; 材料科学 (cond-mat.mtrl-sci) ; 其他凝聚态物理 (cond-mat.other) ; 应用物理 (physics.app-ph)
非晶固体如玻璃中剪切带的形成一直是我们在凝聚态和非晶材料理解中的一个开放性问题。 与晶体不同，由于原子层面缺乏周期性有序背景，像位错这样的明确拓扑缺陷一直难以捉摸。 最近，已经在非晶固体的位移场和特征向量中识别出了拓扑缺陷。 最近的研究表明，非晶固体中的剪切带与涡旋-反涡旋偶极子的对齐一致，具有交替的拓扑电荷+1/-1。 在这里，我们通过二维的受控模拟数值验证了这一假设。 令人惊讶的是，我们展示了在剪切带出现之前就存在一个拓扑缺陷（TD）链，并且在弹性区域的非仿射位移场中已经可见。 当远离TD链的偶极子消失并可能湮灭时，这条链被激活为一个流动带。 可能的潜在机制类似于一种类似孤子的稀疏脉冲，由偶极子湮灭远程激活，这在超流体玻色-爱因斯坦凝聚体中已被观察到。
The formation of shear bands in amorphous solids such as glasses has remained an open question in our understanding of condensed matter and amorphous materials. Unlike in crystals, well-defined topological defects such as dislocations have been elusive due to the lack of a periodic ordered background at the atomic level. Recently, topological defects have been identified in the displacement field and in the eigenvectors of amorphous solids. Recent work has suggested that shear bands in amorphous solids coincide with an alignment of vortex-antivortex dipoles, with alternating topological charge +1/-1. Here we numerically confirm this hypothesis by means of well-controlled simulations in 2D. Surprisingly, we show that a chain of topological defects (TDs) pre-exists the shear band and is visible already in the non-affine displacement field of the elastic regime. This chain is activated into a flow band concomitantly with the disappearance and possibly annihilation of a dipole at a distance from the TDs chain. The possible underlying mechanism is reminiscent of a soliton-like rarefaction pulse remotely activated by dipole annihilation as observed in superfluid Bose-Einstein condensates.
- [13] arXiv:2507.12312 (替换) [中文pdf, pdf, html, 其他]
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标题： 当$B_2$不够时：评估简单指标预测内在无序蛋白质相分离的能力标题： When $B_2$ is Not Enough: Evaluating Simple Metrics for Predicting Phase Separation of Intrinsically Disordered Proteins评论： 46页，7图，支持信息主题： 软凝聚态物理 (cond-mat.soft) ; 统计力学 (cond-mat.stat-mech) ; 定量方法 (q-bio.QM)
理解并预测固有无序蛋白质（IDPs）的相行为在许多生物过程中具有重要意义。然而，有效表征相行为及其对蛋白质一级序列的复杂依赖性仍然具有挑战性。在本研究中，我们评估了几种简单的计算指标的有效性，以量化单组分IDP溶液发生相分离的倾向；所考虑的具体指标包括单链回转半径、第二维里系数以及一种新提出的称为消耗密度的量。每个指标都是通过粗粒度分子动力学模拟计算的，针对2,034个IDP序列。利用机器学习，我们分析这些数据以了解序列特征如何与每个指标的预测性能相关，并深入了解它们各自的优缺点。确定消耗密度是一个广泛有用的指标，它结合了简单性、低计算成本和准确性；它还提供了一个连续的度量，在相分离和非相分离序列中都具有信息量。此外，该指标在提高IDP系统其他性质的预测能力方面显示出前景。这项工作通过超越二元分类扩展了现有文献，这在快速筛选相行为或预测与IDP相关的系统其他性质时可能有用。
Understanding and predicting the phase behavior of intrinsically disordered proteins (IDPs) is of significant interest due to their role in many biological processes. However, effectively characterizing phase behavior and its complex dependence on protein primary sequence remains challenging. In this study, we evaluate the efficacy of several simple computational metrics to quantify the propensity of single-component IDP solutions to phase separate; specific metrics considered include the single-chain radius of gyration, the second virial coefficient, and a newly proposed quantity termed the expenditure density. Each metric is computed using coarse-grained molecular dynamics simulations for 2,034 IDP sequences. Using machine learning, we analyze this data to understand how sequence features correlate with the predictive performance of each metric and to develop insight into their respective strengths and limitations. The expenditure density is determined to be a broadly useful metric that combines simplicity, low computational cost, and accuracy; it also provides a continuous measure that remains informative across both phase-separating and non-phase-separating sequences. Additionally, this metric shows promise in its ability to improve predictions of other properties for IDP systems. This work extends existing literature by advancing beyond binary classification, which can be useful for rapidly screening phase behavior or predicting other properties of IDP-related systems.
- [14] arXiv:2506.13942 (替换) [中文pdf, pdf, 其他]
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标题： 非融合和平面内动量生成在驻留液滴簇中标题： Non-coalescence and in-plane momentum generation in sessile droplet clusters评论： 摘要已修订以提高清晰度。文档的其余部分没有更改。主题： 流体动力学 (physics.flu-dyn) ; 软凝聚态物理 (cond-mat.soft)
直观上，当接近的液滴接触时会合并。 然而，在某些条件下，由于中间气体薄膜的夹带，它们可能不会融合。 到目前为止，水滴之间的不融合现象是在水滴以相对质心速度运动时的碰撞中观察到的，或者在存在特定促进效应的情况下，如高介入气体压力、表面活性剂或大尺寸液滴（直径$\gtrsim 1~\mathrm{mm}$）的情况下观察到。 在这里，我们在更宽的液滴直径范围内，从毫米级到小至100微米，无需上述任何因素即可观察到水滴之间的不融合。 这种不融合发生在疏水表面上的静置液滴簇中。 当簇中的任何两个液滴融合时，融合液滴的演变界面似乎与簇中的其他相邻液滴接触，但不一定触发进一步的融合。 事实上，这种看似接触可以表现为弹跳相互作用，并且根据液滴的初始几何排列，它可以产生显著的横向动量，从而导致参与液滴的自发平面内自推进。 该过程的能量转换效率对于紧密排列的三个静置液滴簇高达9%，并且随着参与液滴数量的增加而进一步提高。 这种小液滴的自推进揭示了在超疏水表面上滴状冷凝过程中被动液滴去除和表面更新的新途径，在多种应用中至关重要。
Intuitively, droplets in proximity merge when brought into contact. However, under certain conditions, they may not coalesce due to the entrapment of an interstitial gas film. Non-coalescence between water droplets has so far been observed during collisions of droplets moving with relative centroidal velocity, or in the presence of specific enabling effects such as high intervening gas pressures, surfactants, or large droplet sizes (diameter $\gtrsim 1~\mathrm{mm}$). Here, we report non-coalescence between water droplets over a much wider range of droplet diameters, from millimeters to as small as 100 microns, without the need for any of the above factors. Such non-coalescence occurs in sessile droplet clusters on water-repellent surfaces. When any two droplets in a cluster coalesce, the evolving interface of the coalescing droplets comes in apparent contact with other neighbouring droplets in the cluster, but does not necessarily trigger further coalescence. In fact, such apparent contact can manifest as a bouncing interaction, and depending on the initial geometric arrangement of droplets, it can result in significant lateral momentum generation, consequently leading to spontaneous in-plane self-propulsion of the participating droplets. The energy conversion efficiency of this process reaches as high as 9\% for closely packed clusters of three sessile droplets and increases further with an increase in the number of participating droplets. The resulting self-propulsion of such small droplets reveals a new pathway for passive droplet removal and surface renewal during dropwise condensation on superhydrophobic surfaces, critical in multiple applications.
- [15] arXiv:2507.02266 (替换) [中文pdf, pdf, html, 其他]
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标题： 用于描述在小德伯数下由Oldroyd-B模型描述的粘弹性流体中两个球体接近时润滑力的半解析解标题： A semi-analytical solution for the lubrication force between two spheres approaching in viscoelastic fluids described by the Oldroyd-B model under small Deborah numbers评论： 22页，12图主题： 流体动力学 (physics.flu-dyn) ; 软凝聚态物理 (cond-mat.soft)
粘弹性流体在各种工程和生物应用中起着关键作用，其润滑特性受到从微秒到分钟不等的松弛时间的影响。 尽管牛顿流体的润滑机制已经得到很好的确立，但将其扩展到粘弹性材料——特别是在挤压流动条件下——仍较少被研究。 本研究提出了一个半解析解，用于描述在小德博拉数下，两个球体在博杰尔流体中接近时的润滑力。 与之前假设牛顿速度场的工作不同，我们通过润滑理论和量级分析技术，直接从质量-动量守恒和Oldroyd-B本构方程推导出速度分布。 在稳态条件下，由于需要克服第一法向应力差的原始阻力而增加的压力，导致表面间法向力略有增加。 瞬态分析显示，法向润滑力被两个牛顿平台所限制，并且在球体接近或分离时呈非对称性。 我们的研究结果强调了粘弹性在提高承载能力中的作用，并为在博杰尔流体中建模密集颗粒悬浮液提供了新的见解，其中短程相互作用占主导地位。
Viscoelastic fluids play a critical role in various engineering and biological applications, where their lubrication properties are strongly influenced by relaxation times ranging from microseconds to minutes. Although the lubrication mechanism for Newtonian fluids is well-established, its extension to viscoelastic materials - particularly under squeezing flow conditions - remains less explored. This study presents a semi-analytical solution for the lubrication force between two spheres approaching in a Boger fluid under small Deborah numbers. Unlike previous works that assumed a Newtonian velocity field, we derive the velocity profile directly from the mass-momentum conservation and Oldroyd-B constitutive equations using lubrication theory and order-of-magnitude analysis techniques. Under steady-state conditions, viscoelasticity induces a marginal increase in the surface-to-surface normal force as a result of the increased pressure required to overcome the original resistance from the first normal-stress difference. Transient analyses reveal that the normal lubrication force is bounded by two Newtonian plateaus and is nonsymmetric as the spheres approach or separate. Our findings highlight the role of viscoelasticity in improving load capacity and provide new insight for modelling dense particle suspensions in Boger fluids, where short-range interactions dominate.