Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells
We investigate a two-dimensional system of active Brownian dumbbells using molecular dynamics simulations. In this model, each dumbbell is driven by an active force oriented perpendicular to the axis connecting its two constituent beads. We characterize the resulting phase behavior and find that, ac...
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2025-06-01
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| author | Pasquale Digregorio Claudio Basilio Caporusso Lucio Mauro Carenza Giuseppe Gonnella Daniela Moretti Giuseppe Negro Massimiliano Semeraro Antonio Suma |
| author_facet | Pasquale Digregorio Claudio Basilio Caporusso Lucio Mauro Carenza Giuseppe Gonnella Daniela Moretti Giuseppe Negro Massimiliano Semeraro Antonio Suma |
| author_sort | Pasquale Digregorio |
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| description | We investigate a two-dimensional system of active Brownian dumbbells using molecular dynamics simulations. In this model, each dumbbell is driven by an active force oriented perpendicular to the axis connecting its two constituent beads. We characterize the resulting phase behavior and find that, across all values of activity, the system undergoes phase separation between dilute and dense phases. The dense phase exhibits hexatic order, and for large enough activity, we observe a marked increase in local polarization, with dumbbells predominantly oriented towards the interior of the clusters. Compared to the case of axially self-propelled dumbbells, we find that the binodal region is enlarged towards lower densities at all activities. This shift arises because dumbbells with transverse propulsion can more easily form stable cluster cores, serving as nucleation seeds, and show a highly suppressed escaping rate from the cluster boundary. Finally, we observe that clusters exhibit spontaneous rotation, with the modulus of the angular velocity scaling as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>∼</mo><msubsup><mi>r</mi><mi>g</mi><mrow><mo>−</mo><mn>2</mn></mrow></msubsup></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>g</mi></msub></semantics></math></inline-formula> is the cluster’s radius of gyration. This contrasts with axially propelled dumbbells, where the scaling follows <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>∼</mo><msubsup><mi>r</mi><mi>g</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></mrow></semantics></math></inline-formula>. We develop a simplified analytical model to rationalize this scaling behavior. |
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| spelling | doaj-art-985e6e762e9d498692f09e2d47ab107f2025-08-20T03:32:26ZengMDPI AGEntropy1099-43002025-06-0127769210.3390/e27070692Transverse Self-Propulsion Enhances the Aggregation of Active DumbbellsPasquale Digregorio0Claudio Basilio Caporusso1Lucio Mauro Carenza2Giuseppe Gonnella3Daniela Moretti4Giuseppe Negro5Massimiliano Semeraro6Antonio Suma7Dipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalySUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, UKDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyDipartimento Interateneo di Fisica, Università Degli Studi di Bari and INFN, Sezione di Bari, Via Amendola 173, 70126 Bari, ItalyWe investigate a two-dimensional system of active Brownian dumbbells using molecular dynamics simulations. In this model, each dumbbell is driven by an active force oriented perpendicular to the axis connecting its two constituent beads. We characterize the resulting phase behavior and find that, across all values of activity, the system undergoes phase separation between dilute and dense phases. The dense phase exhibits hexatic order, and for large enough activity, we observe a marked increase in local polarization, with dumbbells predominantly oriented towards the interior of the clusters. Compared to the case of axially self-propelled dumbbells, we find that the binodal region is enlarged towards lower densities at all activities. This shift arises because dumbbells with transverse propulsion can more easily form stable cluster cores, serving as nucleation seeds, and show a highly suppressed escaping rate from the cluster boundary. Finally, we observe that clusters exhibit spontaneous rotation, with the modulus of the angular velocity scaling as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>∼</mo><msubsup><mi>r</mi><mi>g</mi><mrow><mo>−</mo><mn>2</mn></mrow></msubsup></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>r</mi><mi>g</mi></msub></semantics></math></inline-formula> is the cluster’s radius of gyration. This contrasts with axially propelled dumbbells, where the scaling follows <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>∼</mo><msubsup><mi>r</mi><mi>g</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></mrow></semantics></math></inline-formula>. We develop a simplified analytical model to rationalize this scaling behavior.https://www.mdpi.com/1099-4300/27/7/692active matterself-propelled dumbbellsphase diagrammotility-induced phase separation |
| spellingShingle | Pasquale Digregorio Claudio Basilio Caporusso Lucio Mauro Carenza Giuseppe Gonnella Daniela Moretti Giuseppe Negro Massimiliano Semeraro Antonio Suma Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells Entropy active matter self-propelled dumbbells phase diagram motility-induced phase separation |
| title | Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells |
| title_full | Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells |
| title_fullStr | Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells |
| title_full_unstemmed | Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells |
| title_short | Transverse Self-Propulsion Enhances the Aggregation of Active Dumbbells |
| title_sort | transverse self propulsion enhances the aggregation of active dumbbells |
| topic | active matter self-propelled dumbbells phase diagram motility-induced phase separation |
| url | https://www.mdpi.com/1099-4300/27/7/692 |
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