Density and structural anomalies in soft-repulsive dimeric fluids

TL;DR

This study uses Monte Carlo simulations to explore how dimer shape and potential softness influence density and structural anomalies in fluids, revealing that non-spherical molecules can exhibit such anomalies even without two distinct interaction length scales.

Contribution

It demonstrates that dimeric particles with softened repulsive potentials show density and structural anomalies, highlighting the roles of shape and interaction parameters in anomalous fluid behavior.

Findings

Density and structural anomalies occur without two-length-scale interactions.

Anomalies diminish with increasing dimer aspect ratio.

Structural anomalies can persist after density anomalies disappear.

Abstract

We report Monte Carlo results for the fluid structure of a system of dimeric particles interacting via a core-softened potential. More specifically, dimers interact through a repulsive pair potential of inverse-power form, modified in such a way that the repulsion strength is softened in a given range of distances. The aim of such a study is to investigate how both the elongation of the dimers and the softness of the potential affect some features of the model. Our results show that the dimeric fluid exhibits both density and structural anomalies even if the interaction is not characterized by two length scales. Upon increasing the aspect ratio of the dimers, such anomalies are progressively hindered, with the structural anomaly surviving even after the disappearance of the density anomaly. These results shed light on the peculiar behaviour of molecular systems of non-spherical shape, showing how geometrical and interaction parameters play a fundamental role for the presence of anomalies.