Which mechanism underlies the water-like anomalies in core-softened potentials?

TL;DR

This study uses molecular dynamics to compare water-like anomalies in continuous and discrete core-softened potentials, revealing anomalies only in the continuous case and linking them to excess entropy effects.

Contribution

It demonstrates that water-like anomalies occur only in continuous core-softened potentials, providing insight into the underlying mechanisms.

Findings

Anomalies in density and diffusion are present in continuous potentials.

Discrete potentials do not exhibit these anomalies.

Anomalies are linked to excess entropy effects.

Abstract

Using molecular dynamics simulations we investigate the thermodynamic of particles interacting with a continuous and a discrete versions of a core-softened (CS) intermolecular potential composed by a repulsive shoulder. Dynamic and structural properties are also analyzed by the simulations. We show that in the continuous version of the CS potential the density at constant pressure has a maximum for a certain temperature. Similarly the diffusion constant, $D$, at a constant temperature has a maximum at a density $\rho_{\mathrm{max}}$ and a minimum at a density $\rho_{\mathrm{min}}<\rho_{\mathrm{max}}$, and structural properties are also anomalous. For the discrete CS potential none of these anomalies are observed. The absence of anomalies in the discrete case and its presence in the continuous CS potential are discussed in the framework of the excess entropy.