Phase transitions and cluster structures of the new finite range Lennard-Jones like model

TL;DR

This study investigates a finite-range Lennard-Jones-like potential, analyzing its phase transitions, cluster structures, and thermodynamic properties using nested sampling, revealing complex effects of interaction range on condensed matter behavior.

Contribution

It introduces a well-defined finite-range potential and maps its phase diagram, showing how interaction range influences structural and thermodynamic properties.

Findings

Longer interaction ranges lead to liquid-vapor coexistence and critical points.

Different close-packed phases are stable at various pressures and cutoffs.

Cluster structures resemble Morse potential minima at certain sizes.

Abstract

In the current work we revisit the pair-potential recently proposed by Wang et al. (Phys. Chem. Chem. Phys. 10624, 22, 2020) as a well defined finite-range alternative to the widely used Lennard-Jones interaction model. The advantage of their proposed potential is that it not only goes smoothly to zero at the cutoff distance, hence eliminating inconsistencies caused by different treatments of the truncation, but with changing the range of the potential, it is capable of describing soft matter-like behaviour as well as traditional "Lennard-Jones-like" properties. We used the nested sampling method to perform an unbiased sampling of the potential energy surface, and mapped the pressure-temperature phase diagram of a range of truncation distances. We found that the interplay between the location of the energy minimum and interaction range has a complex and strong effect on both the structural and thermodynamic properties of the condensed phases. We discuss the appearance of the liquid-vapour co-existence line and critical point at longer interaction ranges, as well as the relatively small changes in the melting line. We present the ground state diagram, demonstrating that different close-packed polytypic phases appear to be global minima for the model at different pressure and cutoff values, similar to what had been shown in case of the Lennard-Jones model. Finally, we compare the lowest energy structure of some of the N < 60 clusters to that of the known minima of Lennard-Jones and Morse potential, using different cutoff values, revealing a behaviour closely resembling that of the Morse clusters.