Core-softened system with attraction: trajectory dependence of anomalous behavior

Area of Science:

• Physical Chemistry
• Computational Physics
• Soft Matter Physics

Background:

• Core-softened potentials are used to model systems exhibiting anomalous behavior, such as water.
• Understanding the conditions under which these anomalies manifest is crucial for theoretical and experimental studies.

Purpose of the Study:

• To investigate the influence of thermodynamic trajectories on water-like anomalies in a core-softened system.
• To determine the conditions under which diffusion and structural anomalies are observable.
• To assess the applicability of Rosenfeld entropy scaling relations in anomalous regions.

Main Methods:

• Molecular dynamics simulations were performed on a core-softened system.
• The system's behavior was analyzed along various paths in the pressure-density-temperature (P-ρ-T) space, including isotherms, isochores, isobars, and adiabats.
• Kinetic coefficients and excess entropy were calculated to evaluate Rosenfeld scaling relations.

Main Results:

• The visibility of diffusion and structural anomalies is dependent on the chosen thermodynamic trajectory.
• Anomalies are observed along isotherms (as a function of density) but not along isochores or isobars (as a function of temperature).
• Diffusion anomalies can be observed along adiabats (as a function of temperature, density, and pressure).
• The validity of Rosenfeld entropy scaling relations for the diffusion coefficient also depends on the thermodynamic trajectory.

Conclusions:

• The manifestation of water-like anomalies in core-softened systems is critically dependent on the thermodynamic path explored.
• Defining anomalous regions requires examining all possible trajectories, not just individual paths.
• The applicability of Rosenfeld scaling relations is path-dependent, underscoring the complexity of anomalous fluid behavior.