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  • Open Access

Activity and competing length scales in an anomalous core-softened fluid

Davi Felipe Kray Silva

Thiago Puccinelli

Walas Silva-Oliveira

Leandro B. Krott

José Rafael Bordin*

  • Programa de Pós-Graduação em Modelagem Matemática, Instituto de Física e Matemática, Universidade Federal de Pelotas, Caixa Postal 354, CEP 96001-970 Pelotas, RS, Brazil

  • *Contact author: jrbordin@ufpel.edu.br
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Phys. Rev. E 114, 055402 – Published 2 November, 2026

DOI: https://doi.org/10.1103/frfb-nzyz

Abstract

The interplay between activity and competing interaction length scales remains largely unexplored, despite its relevance to many soft and biological systems. Here, we study active Brownian particles interacting through a ramp-like core-softened potential that exhibits water-like anomalies in equilibrium. By varying the activity over a broad range of densities along two representative isotherms, one within the anomalous region and the other above it, we examine how self-propulsion modifies the structure and dynamics of the fluid. To gain local structural insight into how activity modifies local structure, we construct effective interactions from the steady-state pair correlations using iterative Boltzmann inversion. We find that activity progressively suppresses the anomalies of the passive fluid, although signatures of the underlying structural crossover remain visible in normalized quantities. The effective interactions reveal that self-propulsion lowers the distinction between the local environments and facilitates population transfer between the two characteristic length scales. These results indicate that activity primarily acts by facilitating population transfer between the two local environments, thereby reducing the structural competition responsible for the anomalous response.

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Phys. Rev. E 114, 055402– Published 2 November, 2026
  • Received 30 June 2026
  • Accepted 20 October 2026
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