Abstract
Two boundary lines are frequently discussed in the literature, separating state regions dominated by repulsion or attraction. The Fisher-Widom line indicates where the longest-range decay of the total pair correlation function crosses from monotonic to exponentially damped oscillatory. In the context of thermodynamic metric geometry, such a transition exists where the Ricci curvature scalar vanishes, . To establish a possible relation between these two lines, is worked out for four simple fluids. The truncated and shifted Lennard-Jones, a colloid-like and the square-well potential are analyzed to investigate the influence of the repulsive nature on the location of the line. For the longer-ranged Lennard-Jones potential, the influence of the cutoff radius on the line is studied. The results are compared with literature data on the Fisher-Widom line. Since such data are rare for the longer-ranged Lennard-Jones potential, dedicated simulations are carried out to determine the number of zeros of the total correlation function, which may provide approximate information about the position of the Fisher-Widom line. An increase of the repulsive strength toward hard sphere interaction leads to the disappearance of the line in the fluid phase. A rising attraction range results in the nonexistence of the Fisher-Widom line, while it has little effect on the line as long as it is present in the fluid state.
5 More- Received 1 June 2022
- Accepted 12 July 2022
DOI:https://doi.org/10.1103/PhysRevE.106.034136
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