Title: Transient structured fluctuations in a two-dimensional system with multiple ordered phases

Abstract

We report the structure of transient fluctuations in the liquid phase of a two-dimensional system that exhibits several ordered phases with different symmetries. The density-temperature phase diagram of the system studied, composed of particles with a repulsive shouldered soft-core pair interaction, has regions with stable liquid and hexatic phases, a square solid phase, two separate hexagonal solid phases, and a quasi-crystalline phase with 12-fold symmetry. We have examined the character of the structured fluctuations by computing the same-time aperture cross correlation function of particle configurations in several fluid regions near to and far from phase transition lines. The two primary goals of our study are (1) determination if the spectrum of structures of the fluctuations in the liquid is broader than or limited to the motifs exhibited by the ordered phases supported by the system and (2) determination of the density domains in the liquid that support particular transient structured fluctuations. In the system studied, along a low-temperature isotherm in the temperature-density plane that intersects all the ordered phases we find that the liquid phase exhibits structured fluctuations with hexagonal symmetry near both liquid-hexatic transition lines. Along the same isotherm and in the stable liquid between the lower density hexatic-to-liquidmore » and the higher density liquid-to-square solid transitions, we find that transient hexagonal ordered fluctuations dominate the liquid region near the hexatic-to-liquid transition and square ordered fluctuations dominate the liquid region near the liquid-to square solid transition, but both of these structured fluctuations occur at all densities between these transition lines. At a higher temperature, at phase points in the liquid above, but close to the density maximum of an underlying transition, there are ordered fluctuations that can be correlated with the structure of the lower temperature phase. Although it is expected that very close to a liquid-ordered phase boundary a structured fluctuation in the liquid will have the same symmetry as the ordered phase, it is not obvious that structured fluctuations in thermodynamic states deep in the liquid phase will be similarly restricted. The most striking result of our calculations is that no evidence is found in the liquid phase for structured fluctuations with other symmetries than those of the ordered phases of the system.« less

Authors:

Krebs, Zach ^[1]; Roitman, Ari B.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-4671-2591"
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Nowack, Linsey M. ^[1]; Liepold, Chris ^[1]; Lin, Binhua ^[1]; Rice, Stuart A.  ^[1]

• Search DOE PAGES for author "Rice, Stuart A."
• Search DOE PAGES for ORCID "0000-0003-2133-5275"
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+ Show Author Affiliations

1. Univ. of Chicago, IL (United States)

Publication Date:

2018-07-19

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

Sponsoring Org.:

USDOE Office of Science (SC); National Science Foundation (NSF)

OSTI Identifier:

1491893

Grant/Contract Number:  

NSF/CHE-1346572; DMR-1420709; SI-14-014

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 149; Journal Issue: 3; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

ENGLISH

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Statistical mechanics models; Crystal lattices; High-density liquid; Interatomic potentials; Voronoi diagrams; Phase transitions