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Updated: Oct 19, 2025

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Published on: February 15, 2016

Structural analysis of disordered dimer packings.

Esma Kurban¹, Adrian Baule¹

¹School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK. a.baule@qmul.ac.uk.

|September 20, 2021

Summary

Disordered packings of elongated particles like dimers show a peak in density at specific aspect ratios. This density increase is driven by structural changes and rearrangements in particle contacts.

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Area of Science:

Physics
Materials Science
Statistical Mechanics

Background:

Disordered packings of non-spherical particles exhibit variable packing densities dependent on particle shape.
Elongated shapes (ellipsoids, spherocylinders, dimers) pack denser than spheres within a specific aspect ratio range, peaking around α ≈ 1.4-1.5.

Purpose of the Study:

Investigate the underlying structural features responsible for the non-monotonic packing density behavior in elongated particles.
Characterize the structural changes in frictionless dimer packings as a function of aspect ratio.

Main Methods:

Simulated disordered packings of frictionless dimers in 3D using a gravitational pouring protocol in LAMMPS.
Analyzed contact characteristics, orientational order (nematic), and translational order metrics.

Main Results:

Identified significant structural changes in dimer packings up to the peak density aspect ratio (α_max).
Observed reorganization of inter-dimer contact configurations, increased nematic order, and decreased local translational order as aspect ratio increases towards α_max.
Found that structural metrics remained largely constant for aspect ratios beyond α_max.

Conclusions:

The peak packing density in dimer systems is attributed to a combination of structural rearrangements occurring below α_max and stable excluded volume effects with largely unchanged structure above α_max.