We use supervised machine learning together with the concepts of classical density functional theory to investigate the effects of interparticle attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence, and associated interfacial phenomena in many-body systems. Local learning of the one-body direct correlation functional is based on Monte Carlo simulations of inhomogeneous systems with randomized thermodynamic conditions, randomized planar shapes of the external potential, and randomized box sizes. Focusing on the prototypical Lennard-Jones system, we test predictions of the resulting neural attractive density functional across a broad spectrum of physical behaviour associated with liquid-gas phase coexistence in bulk and at interfaces. We analyse the bulk radial distribution function $g(r)$ obtained from automatic differentiation and the Ornstein-Zernike route and determine i) the Fisher-Widom line, i.e. the crossover of the asymptotic (large distance) decay of $g(r)$ from monotonic to oscillatory, ii) the (Widom) line of maximal correlation length, iii) the line of maximal isothermal compressibility and iv) the spinodal by calculating the poles of the structure factor in the complex plane. The bulk binodal and the density profile of the free liquid-gas interface are obtained from density functional minimization and the corresponding surface tension from functional line integration. We also show that the neural functional describes accurately the phenomena of drying at a hard wall and of capillary evaporation for a liquid confined in a slit pore. Our neural framework yields results that improve significantly upon standard mean-field treatments of interparticle attraction. Comparison with independent simulation results demonstrates a consistent picture of phase separation even when restricting the training to supercritical states only.
{"title":"Neural density functional theory of liquid-gas phase coexistence","authors":"Florian Sammüller, Matthias Schmidt, Robert Evans","doi":"arxiv-2408.15835","DOIUrl":"https://doi.org/arxiv-2408.15835","url":null,"abstract":"We use supervised machine learning together with the concepts of classical\u0000density functional theory to investigate the effects of interparticle\u0000attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence,\u0000and associated interfacial phenomena in many-body systems. Local learning of\u0000the one-body direct correlation functional is based on Monte Carlo simulations\u0000of inhomogeneous systems with randomized thermodynamic conditions, randomized\u0000planar shapes of the external potential, and randomized box sizes. Focusing on\u0000the prototypical Lennard-Jones system, we test predictions of the resulting\u0000neural attractive density functional across a broad spectrum of physical\u0000behaviour associated with liquid-gas phase coexistence in bulk and at\u0000interfaces. We analyse the bulk radial distribution function $g(r)$ obtained\u0000from automatic differentiation and the Ornstein-Zernike route and determine i)\u0000the Fisher-Widom line, i.e. the crossover of the asymptotic (large distance)\u0000decay of $g(r)$ from monotonic to oscillatory, ii) the (Widom) line of maximal\u0000correlation length, iii) the line of maximal isothermal compressibility and iv)\u0000the spinodal by calculating the poles of the structure factor in the complex\u0000plane. The bulk binodal and the density profile of the free liquid-gas\u0000interface are obtained from density functional minimization and the\u0000corresponding surface tension from functional line integration. We also show\u0000that the neural functional describes accurately the phenomena of drying at a\u0000hard wall and of capillary evaporation for a liquid confined in a slit pore.\u0000Our neural framework yields results that improve significantly upon standard\u0000mean-field treatments of interparticle attraction. Comparison with independent\u0000simulation results demonstrates a consistent picture of phase separation even\u0000when restricting the training to supercritical states only.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shivakumar Athani, Bloen Metzger, Yoël Forterre, Romain Mari
Using particle-based numerical simulations performed under pressure-imposed conditions, we investigate the transient dilation dynamics of a shear thickening suspension brought to shear jamming. We show that the stress levels, instead of diverging as predicted by steady state flow rules, remain finite and are entirely determined by the coupling between the particle network dilation and the resulting Darcy backflow. System-spanning stress gradients along the dilation direction lead to cross-system stress differences scaling quadratically with the system size. Measured stress levels are quantitatively captured by a continuum model based on a Reynolds-like dilatancy law and the Wyart-Cates constitutive model. Beyond globally jammed suspensions, our results enable the modeling of inhomogeneous flows where shear jamming is local, e.g. under impact, which eludes usual shear thickening rheological laws.
{"title":"Transients in shear thickening suspensions: when hydrodynamics matters","authors":"Shivakumar Athani, Bloen Metzger, Yoël Forterre, Romain Mari","doi":"arxiv-2408.15130","DOIUrl":"https://doi.org/arxiv-2408.15130","url":null,"abstract":"Using particle-based numerical simulations performed under pressure-imposed\u0000conditions, we investigate the transient dilation dynamics of a shear\u0000thickening suspension brought to shear jamming. We show that the stress levels,\u0000instead of diverging as predicted by steady state flow rules, remain finite and\u0000are entirely determined by the coupling between the particle network dilation\u0000and the resulting Darcy backflow. System-spanning stress gradients along the\u0000dilation direction lead to cross-system stress differences scaling\u0000quadratically with the system size. Measured stress levels are quantitatively\u0000captured by a continuum model based on a Reynolds-like dilatancy law and the\u0000Wyart-Cates constitutive model. Beyond globally jammed suspensions, our results\u0000enable the modeling of inhomogeneous flows where shear jamming is local, e.g.\u0000under impact, which eludes usual shear thickening rheological laws.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The phase behavior of symmetric diblock copolymers under three-dimensional (3D) soft confinement is investigated using the self-consistent field theory. The soft confinement is realized in binary blends composed AB diblock copolymers and C homopolymers, where the copolymers self-assemble to form a droplet embedded in the homopolymer matrix. The phase behavior of the confined block copolymers is regulated by the degree of confinement and the selectivity of the homopolymers, resulting in a rich variety of novel structures. When the C homopolymers are neutral to the A- and B-blocks, stacked lamellae (SL) are formed where the number of layers increases with the droplet volume, resulting in a morphological transition sequence from Janus particle to square SL. When the C homopolymers are strongly selective to the B-blocks, a series of non-lamellar morphologies, including onion-, hamburger-, cross-, ring-, and cookie-like structures, are observed. A detailed free energy analysis reveals a first-order reversible transformation between SL and onion-like (OL) structures when the selectivity of the homopolymers is changed. Our results provide a comprehensive understanding of how various factors, such as the copolymer concentration, homopolymer chain length, degree of confinement, homopolymer selectivity, affect the self-assembled structures of diblock copolymers under soft 3D confinement.
利用自洽场理论研究了对称二嵌段共聚物在三维（3D）软约束下的相行为。软约束是在由AB二嵌段共聚物和C均聚物组成的二元共混物中实现的，共聚物自组装形成嵌入均聚物基体中的小滴。封闭嵌段共聚物的相行为受封闭程度和均聚物选择性的影响，从而产生了丰富多样的新型结构。当 C 均聚物与 A 嵌段和 B 嵌段呈中性时，会形成叠层（SL），层数随液滴体积的增加而增加，从而形成从 Janus 粒子到方形 SL 的形态过渡序列。当 C 均聚物对 B 嵌段具有强选择性时，就会出现一系列非层状形态，包括洋葱状、汉堡状、交叉状、环状和饼干状结构。详细的自由能分析表明，当均聚物的选择性发生改变时，SL 结构和类洋葱（OL）结构之间会发生一阶可逆转变。我们的研究结果让人们全面了解了共聚物浓度、均聚物链长、封闭程度、均聚物选择性等各种因素如何影响二嵌段共聚物在软三维封闭条件下的自组装结构。
{"title":"Phase behavior of symmetric diblock copolymers under 3D soft confinement","authors":"Zhijuan He, Jin Huang, Kai Jiang, An-Chang Shi","doi":"arxiv-2408.14863","DOIUrl":"https://doi.org/arxiv-2408.14863","url":null,"abstract":"The phase behavior of symmetric diblock copolymers under three-dimensional\u0000(3D) soft confinement is investigated using the self-consistent field theory.\u0000The soft confinement is realized in binary blends composed AB diblock\u0000copolymers and C homopolymers, where the copolymers self-assemble to form a\u0000droplet embedded in the homopolymer matrix. The phase behavior of the confined\u0000block copolymers is regulated by the degree of confinement and the selectivity\u0000of the homopolymers, resulting in a rich variety of novel structures. When the\u0000C homopolymers are neutral to the A- and B-blocks, stacked lamellae (SL) are\u0000formed where the number of layers increases with the droplet volume, resulting\u0000in a morphological transition sequence from Janus particle to square SL. When\u0000the C homopolymers are strongly selective to the B-blocks, a series of\u0000non-lamellar morphologies, including onion-, hamburger-, cross-, ring-, and\u0000cookie-like structures, are observed. A detailed free energy analysis reveals a\u0000first-order reversible transformation between SL and onion-like (OL) structures\u0000when the selectivity of the homopolymers is changed. Our results provide a\u0000comprehensive understanding of how various factors, such as the copolymer\u0000concentration, homopolymer chain length, degree of confinement, homopolymer\u0000selectivity, affect the self-assembled structures of diblock copolymers under\u0000soft 3D confinement.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Despite many efforts, the fracture of network polymers under extension is yet to be elucidated. This study investigated the effect of strand molecular weight on the fracture characteristics of the networks made from star-branched prepolymers with various node functionalities $3 le f le 8$ and conversion ratios $0.6 le {phi}_c le 0.95$ via molecular simulations with phantom chains. The networks were created via end-linking reactions of star polymers with the arm molecular weight $N_a$ = 2, 5, and 10, simulated by a Brownian dynamics scheme. The cycle rank of the percolated network ${xi}$ was entirely consistent with the mean-field theory, implying that the reaction occurred independently and the network connectivity was statistically fair. Afterward, the networks were alternatively subjected to energy minimization and uniaxial stretch until the break. From the stress-strain curves recorded during the stretch, the stretch and stress at the break, ${lambda}_b$ and ${sigma}_b$, and work for fracture $W_b$ were obtained. For these values, the following relations were found: ${lambda}_b sim N_a^{(1/2)} {xi}^{(-1/3)}$, ${sigma}_b sim {nu}_{br} N_a^{(4/3)} {xi}^{(2/3)}$, and $W_b sim {nu}_{br} N_a^{(4/3)} {xi}^{(2/3)}$, where ${nu}_{br}$ is the branch point density.
尽管做了很多努力，但网络聚合物在延伸条件下的断裂仍有待阐明。本研究通过使用幻影链进行分子模拟，研究了股分子量对不同节点官能度为 $3 le f le 8$ 和转化率为 $0.6 le {phi}_c le 0.95$ 的星形支链聚合物网络断裂特性的影响。这些网络是通过臂分子量为 N_a$ = 2、5 和 10 的星型聚合物的端接反应生成的，并通过布朗动力学方案进行了模拟。渗流网络的循环等级 ${xi}$ 与均场理论完全一致，这意味着反应的发生是独立的，网络的连通性在统计学上是公平的。随后，对网络分别进行了能量最小化和单轴拉伸试验，直至断裂。根据拉伸过程中记录的应力-应变曲线，得到了断裂处的拉伸和应力 ${lambda}_b$ 和 ${sigma}_b$ 以及断裂功 $W_b$。对于这些值，我们发现了以下关系：${lambda}_b sim N_a^{(1/2)} {xi}^{(-1/3)}$, ${sigma}_b sim {nu}_{br}.N_a^{(4/3)}{xi}^{(2/3)}$，以及 $W_b sim{nu}_{br}其中 ${nu}_{br}$ 是分支点密度。
{"title":"Phantom chain simulations for fracture of star polymer networks on the effect of arm molecular weight","authors":"Yuichi Masubuchi","doi":"arxiv-2408.14058","DOIUrl":"https://doi.org/arxiv-2408.14058","url":null,"abstract":"Despite many efforts, the fracture of network polymers under extension is yet\u0000to be elucidated. This study investigated the effect of strand molecular weight\u0000on the fracture characteristics of the networks made from star-branched\u0000prepolymers with various node functionalities $3 le f le 8$ and conversion\u0000ratios $0.6 le {phi}_c le 0.95$ via molecular simulations with phantom\u0000chains. The networks were created via end-linking reactions of star polymers\u0000with the arm molecular weight $N_a$ = 2, 5, and 10, simulated by a Brownian\u0000dynamics scheme. The cycle rank of the percolated network ${xi}$ was entirely\u0000consistent with the mean-field theory, implying that the reaction occurred\u0000independently and the network connectivity was statistically fair. Afterward,\u0000the networks were alternatively subjected to energy minimization and uniaxial\u0000stretch until the break. From the stress-strain curves recorded during the\u0000stretch, the stretch and stress at the break, ${lambda}_b$ and ${sigma}_b$,\u0000and work for fracture $W_b$ were obtained. For these values, the following\u0000relations were found: ${lambda}_b sim N_a^{(1/2)} {xi}^{(-1/3)}$,\u0000${sigma}_b sim {nu}_{br} N_a^{(4/3)} {xi}^{(2/3)}$, and $W_b sim\u0000{nu}_{br} N_a^{(4/3)} {xi}^{(2/3)}$, where ${nu}_{br}$ is the branch point\u0000density.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"172 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Saptorshi Ghosh, Aparna Baskaran, Michael F. Hagan
Being intrinsically nonequilibrium, active materials can potentially perform functions that would be thermodynamically forbidden in passive materials. However, active systems have diverse local attractors that correspond to distinct dynamical states, many of which exhibit chaotic turbulent-like dynamics and thus cannot perform work or useful functions. Designing such a system to choose a specific dynamical state is a formidable challenge. Motivated by recent advances enabling opto-genetic control of experimental active materials, we describe an optimal control theory framework that identifies a spatiotemporal sequence of light-generated activity that drives an active nematic system toward a prescribed dynamical steady-state. Active nematics are unstable to spontaneous defect proliferation and chaotic streaming dynamics in the absence of control. We demonstrate that optimal control theory can compute activity fields that redirect the dynamics into a variety of alternative dynamical programs and functions. This includes dynamically reconfiguring between states, and selecting and stabilizing emergent behaviors that do not correspond to attractors, and are hence unstable in the uncontrolled system. Our results provide a roadmap to leverage optical control methods to rationally design structure, dynamics, and function in a wide variety of active materials.
{"title":"Achieving designed texture and flows in bulk active nematics using optimal control theory","authors":"Saptorshi Ghosh, Aparna Baskaran, Michael F. Hagan","doi":"arxiv-2408.14596","DOIUrl":"https://doi.org/arxiv-2408.14596","url":null,"abstract":"Being intrinsically nonequilibrium, active materials can potentially perform\u0000functions that would be thermodynamically forbidden in passive materials.\u0000However, active systems have diverse local attractors that correspond to\u0000distinct dynamical states, many of which exhibit chaotic turbulent-like\u0000dynamics and thus cannot perform work or useful functions. Designing such a\u0000system to choose a specific dynamical state is a formidable challenge.\u0000Motivated by recent advances enabling opto-genetic control of experimental\u0000active materials, we describe an optimal control theory framework that\u0000identifies a spatiotemporal sequence of light-generated activity that drives an\u0000active nematic system toward a prescribed dynamical steady-state. Active\u0000nematics are unstable to spontaneous defect proliferation and chaotic streaming\u0000dynamics in the absence of control. We demonstrate that optimal control theory\u0000can compute activity fields that redirect the dynamics into a variety of\u0000alternative dynamical programs and functions. This includes dynamically\u0000reconfiguring between states, and selecting and stabilizing emergent behaviors\u0000that do not correspond to attractors, and are hence unstable in the\u0000uncontrolled system. Our results provide a roadmap to leverage optical control\u0000methods to rationally design structure, dynamics, and function in a wide\u0000variety of active materials.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Evaporation alters the molecular interactions and leads to phase separation within the evaporating liquid. The question of whether evaporation could lead to specific phase separation at the liquid interface and eventually to the formation of patterns in small liquid volumes remains unaddressed. In this study, we investigated the liquid-liquid phase separation (LLPS) of an organic polymeric monomer in a salt-containing buffer within an evaporating sessile droplet. We observed that LLPS occurs at the dynamic interface of the droplet and leads to the formation of polymeric coacervates or regular lattice patterns depending on the initial concentration of the polymer. Our results show that the interaction of salt with the polymeric monomers at the droplet interface can lead to LLPS and the formation of regular patterns. This study suggests that the sessile droplet setup can be utilized to achieve very regular patterns as a result of LLPS.
{"title":"Liquid-liquid phase separation at the interface of an evaporating droplet; formation of a regular lattice pattern","authors":"Vahid Nasirimarekani","doi":"arxiv-2408.14129","DOIUrl":"https://doi.org/arxiv-2408.14129","url":null,"abstract":"Evaporation alters the molecular interactions and leads to phase separation\u0000within the evaporating liquid. The question of whether evaporation could lead\u0000to specific phase separation at the liquid interface and eventually to the\u0000formation of patterns in small liquid volumes remains unaddressed. In this\u0000study, we investigated the liquid-liquid phase separation (LLPS) of an organic\u0000polymeric monomer in a salt-containing buffer within an evaporating sessile\u0000droplet. We observed that LLPS occurs at the dynamic interface of the droplet\u0000and leads to the formation of polymeric coacervates or regular lattice patterns\u0000depending on the initial concentration of the polymer. Our results show that\u0000the interaction of salt with the polymeric monomers at the droplet interface\u0000can lead to LLPS and the formation of regular patterns. This study suggests\u0000that the sessile droplet setup can be utilized to achieve very regular patterns\u0000as a result of LLPS.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John Berezney, Sattvic Ray, Itamar Kolvin, Mark Bowick, Seth Fraden, Zvonimir Dogic
We use the chaotic flows generated by a microtubule-based active fluid to assemble self-binding actin filaments into a thin elastic sheets. Starting from a uniformly dispersed state, active flows drive the motion of actin filaments, inducing their bundling and formation of bundle-bundle connections that ultimately generate an elastic network. The emerging network separates from the active fluid to form a thin elastic sheets suspended at the sample midplane. At intermediate times, the active fluid drives large in-plane and out-of-plane deformations of the elastic sheet which are driven by low-energy bending modes. Self-organized sheets eventually exhibit centimeter-sized global spontaneous oscillations and traveling waves, despite being isotropically driven on micron lengths by the active fluid. The active assembly generates diverse network structures which are not easily realizable with conventional paradigms of equilibrium self-assembly and materials processing. Self-organized mechanical sheets pose a challenge for understanding of how a hierarchy of structure, mechanics, and dynamics emerges from a largely structureless initial suspension of active and passive microscopic components.
{"title":"Controlling assembly and oscillations of elastic membranes with an active fluid","authors":"John Berezney, Sattvic Ray, Itamar Kolvin, Mark Bowick, Seth Fraden, Zvonimir Dogic","doi":"arxiv-2408.14699","DOIUrl":"https://doi.org/arxiv-2408.14699","url":null,"abstract":"We use the chaotic flows generated by a microtubule-based active fluid to\u0000assemble self-binding actin filaments into a thin elastic sheets. Starting from\u0000a uniformly dispersed state, active flows drive the motion of actin filaments,\u0000inducing their bundling and formation of bundle-bundle connections that\u0000ultimately generate an elastic network. The emerging network separates from the\u0000active fluid to form a thin elastic sheets suspended at the sample midplane. At\u0000intermediate times, the active fluid drives large in-plane and out-of-plane\u0000deformations of the elastic sheet which are driven by low-energy bending modes.\u0000Self-organized sheets eventually exhibit centimeter-sized global spontaneous\u0000oscillations and traveling waves, despite being isotropically driven on micron\u0000lengths by the active fluid. The active assembly generates diverse network\u0000structures which are not easily realizable with conventional paradigms of\u0000equilibrium self-assembly and materials processing. Self-organized mechanical\u0000sheets pose a challenge for understanding of how a hierarchy of structure,\u0000mechanics, and dynamics emerges from a largely structureless initial suspension\u0000of active and passive microscopic components.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Mohammad Mousavi, Ida Ang, Jason Mulderrig, Nikolaos Bouklas
Recently, the phase field method has been increasingly used for brittle fractures in soft materials like polymers, elastomers, and biological tissues. When considering finite deformations to account for the highly deformable nature of soft materials, the convergence of the phase-field method becomes challenging, especially in scenarios of unstable crack growth. To overcome these numerical difficulties, several approaches have been introduced, with artificial viscosity being among the most widely utilized. This study investigates the energy release rate due to crack propagation in hyperelastic nearly-incompressible materials and compares the phase-field method and a novel gradient-enhanced damage (GED) approach. First, we simulate unstable loading scenarios using the phase-field method, which leads to convergence problems. To address these issues, we introduce artificial viscosity to stabilize the problem and analyze its impact on the energy release rate utilizing a domain J-integral approach giving quantitative measurements during crack propagation. It is observed that the measured energy released rate during crack propagation does not comply with the imposed critical energy release rate, and shows non-monotonic behavior. In the second part of the paper, we introduce a novel stretch-based GED model as an alternative to the phase-field method for modeling crack evolution in elastomers. It is demonstrated that in this method, the energy release rate can be obtained as an output of the simulation rather than as an input which could be useful in the exploration of rate-dependent responses, as one could directly impose chain-level criteria for damage initiation. We show that while this novel approach provides reasonable results for fracture simulations, it still suffers from some numerical issues that strain-based GED formulations are known to be susceptible to.
{"title":"Evaluating fracture energy predictions using phase-field and gradient-enhanced damage models for elastomers","authors":"S. Mohammad Mousavi, Ida Ang, Jason Mulderrig, Nikolaos Bouklas","doi":"arxiv-2408.05162","DOIUrl":"https://doi.org/arxiv-2408.05162","url":null,"abstract":"Recently, the phase field method has been increasingly used for brittle\u0000fractures in soft materials like polymers, elastomers, and biological tissues.\u0000When considering finite deformations to account for the highly deformable\u0000nature of soft materials, the convergence of the phase-field method becomes\u0000challenging, especially in scenarios of unstable crack growth. To overcome\u0000these numerical difficulties, several approaches have been introduced, with\u0000artificial viscosity being among the most widely utilized. This study\u0000investigates the energy release rate due to crack propagation in hyperelastic\u0000nearly-incompressible materials and compares the phase-field method and a novel\u0000gradient-enhanced damage (GED) approach. First, we simulate unstable loading\u0000scenarios using the phase-field method, which leads to convergence problems. To\u0000address these issues, we introduce artificial viscosity to stabilize the\u0000problem and analyze its impact on the energy release rate utilizing a domain\u0000J-integral approach giving quantitative measurements during crack propagation.\u0000It is observed that the measured energy released rate during crack propagation\u0000does not comply with the imposed critical energy release rate, and shows\u0000non-monotonic behavior. In the second part of the paper, we introduce a novel\u0000stretch-based GED model as an alternative to the phase-field method for\u0000modeling crack evolution in elastomers. It is demonstrated that in this method,\u0000the energy release rate can be obtained as an output of the simulation rather\u0000than as an input which could be useful in the exploration of rate-dependent\u0000responses, as one could directly impose chain-level criteria for damage\u0000initiation. We show that while this novel approach provides reasonable results\u0000for fracture simulations, it still suffers from some numerical issues that\u0000strain-based GED formulations are known to be susceptible to.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Akie Kowaguchi, Savan Mehta, Jonathan P. K. Doye, Eva G. Noya
We devise an ideal 3-dimensional octagonal quasicrystal that is based upon the 2-dimensional Ammann-Beenker tiling and that is potentially suitable for realization with patchy particles. Based on an analysis of its local environments we design a binary system of 8- and 5-patch particles that in simulations assembles into a 3-dimensional octagonal quasicrystal. The local structure is subtly different from the original ideal quasicrystal possessing a narrower coordination-number distribution; in fact, the 8-patch particles are not needed and a one-component system of the 5-patch particles assembles into an essentially identical octagonal quasicrystal. We also consider a one-component system of the 8-patch particles; this assembles into a cluster with a number of crystalline domains, but which, because of the coherent boundaries between the crystallites, has approximate eight-fold order. We envisage that these systems could be realized using DNA origami or protein design.
{"title":"A patchy-particle 3-dimensional octagonal quasicrystal","authors":"Akie Kowaguchi, Savan Mehta, Jonathan P. K. Doye, Eva G. Noya","doi":"arxiv-2408.05003","DOIUrl":"https://doi.org/arxiv-2408.05003","url":null,"abstract":"We devise an ideal 3-dimensional octagonal quasicrystal that is based upon\u0000the 2-dimensional Ammann-Beenker tiling and that is potentially suitable for\u0000realization with patchy particles. Based on an analysis of its local\u0000environments we design a binary system of 8- and 5-patch particles that in\u0000simulations assembles into a 3-dimensional octagonal quasicrystal. The local\u0000structure is subtly different from the original ideal quasicrystal possessing a\u0000narrower coordination-number distribution; in fact, the 8-patch particles are\u0000not needed and a one-component system of the 5-patch particles assembles into\u0000an essentially identical octagonal quasicrystal. We also consider a\u0000one-component system of the 8-patch particles; this assembles into a cluster\u0000with a number of crystalline domains, but which, because of the coherent\u0000boundaries between the crystallites, has approximate eight-fold order. We\u0000envisage that these systems could be realized using DNA origami or protein\u0000design.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The particle contact model is important for powder simulations. Although several contact models have been proposed, their validity has not yet been well established. Therefore, we perform molecular dynamics (MD) simulations to clarify the particle interaction. We simulate head-on collisions of two particles with impact velocities less than a few percent of the sound velocity to investigate the dependence of the interparticle force and the coefficient of restitution (COR) on the impact velocity and particle radius. In this study, we treat particles with a radius of 10-100 nm and perform simulations. We find that the interparticle force exhibits hysteresis between the loading and unloading phases. Larger impact velocities result in strong hysteresis and plastic deformation. For all impact velocities and particle radii, the coefficient of restitution is smaller than that given by the Johnson-Kendall-Robert theory. An inelastic contact model cannot reproduce our MD simulations. In particular, the COR is significantly reduced when the impact velocity exceeds a certain value. This significant energy dissipation cannot be explained even by the contact models including plastic deformation. We also find that the COR increases with increasing particle radius. We also find that the previous contact models including plastic deformation cannot explain the strong energy dissipation obtained in our MD simulations, although they agree with the MD results for very low impact velocities. Accordingly, we have constructed a new dissipative contact model in which the dissipative force increases with the stress generated by collisions. The new stress dependent model successfully reproduces our MD results over a wider range of impact velocities than the conventional models do. In addition, we proposed another, simpler, dissipative contact model that can also reproduce the MD results.
{"title":"Molecular dynamics simulations of head-on low-velocity collisions between particles","authors":"Yuki Yoshida, Eiichiro Kokubo, Hidekazu Tanaka","doi":"arxiv-2408.04164","DOIUrl":"https://doi.org/arxiv-2408.04164","url":null,"abstract":"The particle contact model is important for powder simulations. Although\u0000several contact models have been proposed, their validity has not yet been well\u0000established. Therefore, we perform molecular dynamics (MD) simulations to\u0000clarify the particle interaction. We simulate head-on collisions of two\u0000particles with impact velocities less than a few percent of the sound velocity\u0000to investigate the dependence of the interparticle force and the coefficient of\u0000restitution (COR) on the impact velocity and particle radius. In this study, we\u0000treat particles with a radius of 10-100 nm and perform simulations. We find\u0000that the interparticle force exhibits hysteresis between the loading and\u0000unloading phases. Larger impact velocities result in strong hysteresis and\u0000plastic deformation. For all impact velocities and particle radii, the\u0000coefficient of restitution is smaller than that given by the\u0000Johnson-Kendall-Robert theory. An inelastic contact model cannot reproduce our\u0000MD simulations. In particular, the COR is significantly reduced when the impact\u0000velocity exceeds a certain value. This significant energy dissipation cannot be\u0000explained even by the contact models including plastic deformation. We also\u0000find that the COR increases with increasing particle radius. We also find that\u0000the previous contact models including plastic deformation cannot explain the\u0000strong energy dissipation obtained in our MD simulations, although they agree\u0000with the MD results for very low impact velocities. Accordingly, we have\u0000constructed a new dissipative contact model in which the dissipative force\u0000increases with the stress generated by collisions. The new stress dependent\u0000model successfully reproduces our MD results over a wider range of impact\u0000velocities than the conventional models do. In addition, we proposed another,\u0000simpler, dissipative contact model that can also reproduce the MD results.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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