Active Brownian Equation of State: Metastability and Phase Coexistence

Levis, Demian; Codina, Josep; Pagonabarraga, Ignacio

doi:10.48550/arxiv.1703.02412

Cited by 3 publications

(10 citation statements)

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“…We now turn to the discussion of the active hard-disk system with rotational diffusivity D r = 1. For self-propulsion velocities v 0 that are below the onset of motility-induced phase separation (estimated to be around v 0 = 12 in the present system [17]), a similar evolution of S(q) with increasing packing fraction is seen as in the passive system. This case is shown in Fig.…”

Section: Active Hard Diskssupporting

confidence: 62%

“…Note however that for strong self-propulsion and/or fast reorientational diffusion, significantly smaller time steps may be required. The extension to active particles has been used to study glassy dynamics of dense AHS systems [18], and more recently also MIPS [17].…”

Section: Methods and Techniquesmentioning

confidence: 99%

“…This phenomenon is called motilityinduced phase separation (MIPS) as it shares a number of qualitative features with the liquid-gas phase separation known from equilibrium fluids. MIPS has been studied in great detail for various spherical ABP models with different interactions between the particles [14,15,16], since recently also including the hard-sphere case (using the same simulation algorithm as ours) [17]. Here we deliberately restrict our attention to the homogeneous fluid state outside the spinodal of MIPS.…”

Section: Introductionmentioning

confidence: 99%

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Static structure of active Brownian hard disks

Biniossek

Löwen

Voigtmann

et al. 2018

J. Phys.: Condens. Matter

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Abstract. We explore the changes in static structure of a two-dimensional system of active Brownian particles (ABP) with hard-disk interactions, using event-driven Brownian dynamics simulations. In particular, the effect of the selfpropulsion velocity and the rotational diffusivity on the orientationally-averaged fluid structure factor is discussed. Typically activity increases structural ordering and generates a structure factor peak at zero wave vector which is a precursor of motility-induced phase separation. Our results provide reference data to test future statistical theories for the fluid structure of active Brownian systems.

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Section: Active Hard Diskssupporting

confidence: 62%

Section: Methods and Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Static structure of active Brownian hard disks

Biniossek

Löwen

Voigtmann

et al. 2018

J. Phys.: Condens. Matter

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“…As shown in the snapshot and confirmed by the pair-correlation function, particles in the drop are closed packed, showing a highly ordered solid-like structure. Such a compact structure in the absence of attractive interactions is reminiscent to the dense phase generated by MIPS [17,20]. Here, however, it occurs well below the expected critical point for MIPS.…”

mentioning

confidence: 83%

“…While micro-flock patterns emerge as a direct consequence of the interplay between self-propulsion and alignment interaction among circle swimmers [14] -neither require attractive nor repulsive interactions to emerge -it is important to understand their robustness against excluded volume interactions which are naturally present in any conceivable circle swimmer ensemble. Such excluded volume interactions sometimes act as a key player in active matter: for motility-induced phase separation (MIPS) in particular, they block oppositely moving active particle such that they stay together before rotational diffusion releases them [16]; this mechanism can eventually trigger a phase separation for large enough density and selfpropulsion velocity [17][18][19][20].…”

mentioning

confidence: 99%

Micro-flock patterns and macro-clusters in chiral active Brownian disks

Levis

Liebchen

2018

J. Phys.: Condens. Matter

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Abstract. -Chiral active particles (or self-propelled circle swimmers) feature a rich collective behavior, comprising rotating macro-clusters and micro-flock patterns which consist of phasesynchronized rotating clusters with a characteristic self-limited size. These patterns emerge from the competition of alignment interactions and rotations suggesting that they might occur generically in many chiral active matter systems. However, although excluded volume interactions occur naturally among typical circle swimmers, it is not yet clear if macro-clusters and microflock patterns survive their presence. The present work shows that both types of pattern do survive but feature strongly enhance fluctuations regarding the size and shape of the individual clusters. Despite these fluctuations, we find that the average micro-flock size still follows the same characteristic scaling law as in the absence of excluded volume interactions, i.e. micro-flock sizes scale linearly with the single-swimmer radius.

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Interparticle torques suppress motility-induced phase separation for rodlike particles

Damme

Rodenburg

Roij

et al. 2019

The Journal of Chemical Physics

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To study the role of torque in motility-induced phase separation (MIPS), we simulate a system of self-propelled particles whose shape varies smoothly from isotropic (disks/spheres) to weakly elongated (rods). We construct the phase diagrams of 2D active disks, 3D active spheres and 2D/3D active rods of aspect ratio l/σ = 2. A stability analysis of the homogeneous isotropic phase allows us to predict the onset of MIPS based on the effective swimming speed and rotational diffusion of the particles. Both methods find suppression of MIPS as the particle shape is elongated. We propose a suppression mechanism based on the duration of collisions, and argue that this mechanism can explain both the suppression of MIPS found here for rodlike particles and the enhancement of MIPS found for particles with Vicsek interactions.

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Active Brownian Equation of State: Metastability and Phase Coexistence

Cited by 3 publications

References 0 publications

Static structure of active Brownian hard disks

Static structure of active Brownian hard disks

Micro-flock patterns and macro-clusters in chiral active Brownian disks

Interparticle torques suppress motility-induced phase separation for rodlike particles

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