Isomorph Invariance of Higher-Order Structural Measures in Four Lennard-Jones Systems

• Authors: Mahajabin Rahman, Emory University; Benjamin MGD Carter, Bristol Centre for Functional Nanomaterials; Shibu Saw, Roskilde University; Ian M Douglass, Roskilde University; Lorenzo Costigliola, Roskilde University; Trond S Ingebrigtsen, Roskilde University; Thomas B Schroder, Roskilde University; Ulf R Pedersen, Roskilde University; Jeppe C Dyre, Roskilde University
• Journal Title: MOLECULES
• Volume: Volume 26, Number 6
• Publisher: MDPI | 2021-03-01
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.3390/molecules26061746
• Subjects: Physics, General; Environmental Sciences
• Keywords: Science & Technology; Life Sciences & Biomedicine; Physical Sciences; Biochemistry & Molecular Biology; Chemistry, Multidisciplinary; Chemistry; Lennard-Jones system; Voronoi structures; Frank-Kasper bonds; icosahedral local order; bond-orientational order; density scaling; excess entropy; isomorph invariance; hidden scale invariance

Abstract

In the condensed liquid phase, both single-and multicomponent Lennard–Jones (LJ) systems obey the “hidden-scale-invariance” symmetry to a good approximation. Defining an isomorph as a line of constant excess entropy in the thermodynamic phase diagram, the consequent approx-imate isomorph invariance of structure and dynamics in appropriate units is well documented. However, although all measures of the structure are predicted to be isomorph invariant, with few exceptions only the radial distribution function (RDF) has been investigated. This paper studies the variation along isomorphs of the nearest-neighbor geometry quantified by the occurrence of Voronoi structures, Frank–Kasper bonds, icosahedral local order, and bond-orientational order. Data are presented for the standard LJ system and for three binary LJ mixtures (Kob–Andersen, Wahnström, NiY2 ). We find that, while the nearest-neighbor geometry generally varies significantly throughout the phase diagram, good invariance is observed along the isomorphs. We conclude that higher-order structural correlations are no less isomorph invariant than is the RDF.