Percolation in metal-insulator composites of randomly packed spherocylindrical nanoparticles

Abstract

While classical percolation is well understood, percolation effects in randomly packed or jammed structures are much less explored. Here we investigate both experimentally and theoretically the electrical percolation in a binary composite system of disordered spherocylinders, to identify the relation between structural (percolation) and functional properties of nanocomposites. Experimentally, we determine the percolation threshold $p_c$ and the conductivity critical exponent $t$ for composites of conducting (CrO${}_2$) and insulating (Cr${}_2$O${}_3$) rodlike nanoparticles that are nominally geometrically identical, yielding $p_c=0.305\pm 0.026$ and $t=2.52\pm 0.03$ respectively. Simulations and modeling are implemented through a combination of the mechanical contraction method and a variant of random walk (de Gennes ant) approach, in which charge diffusion is correlated with the system conductivity via the Nernst-Einstein relation. The percolation threshold and critical exponents identified through finite size scaling are in good agreement with the experimental values. Curiously, the calculated percolation threshold for spherocylinders with an aspect ratio of 6.5, $p_c=0.312\pm 0.002$, is very close (within numerical errors) to the one found previously in two other distinct systems of disordered jammed spheres and simple cubic lattice, an intriguing and surprising result.

arXiv comment11 pages, 7 figures

References in corpus (16)

• Jammed Hard-Particle Packings: From Kepler to Bernal and Beyond
• Strong scaling of general-purpose molecular dynamics simulations on GPUs
• Andreev Reflection In Ferromagnet-Superconductor Junctions
• Hypoconstrained Jammed Packings of Nonspherical Hard Particles: Ellipses and Ellipsoids
• Tunneling-percolation origin of nonuniversality: theory and experiments
• Exact exponents for the spin quantum Hall transition
• Epidemic threshold for the SIS model on networks
• Scaling corrections: site-percolation and Ising model in three dimensions
• Bond and Site Percolation in Three Dimensions
• Universality of the excess number of clusters and the crossing probability function in three-dimensional percolation
• Scalable Metropolis Monte Carlo for simulation of hard shapes
• Computation of Strained Epitaxial Growth in Three Dimensions by Kinetic Monte Carlo
• Percolation of disordered jammed sphere packings
• Simple cubic random-site percolation thresholds for neighborhoods containing fourth-nearest neighbors
• Percolation thresholds on 3-dimensional lattices with 3 nearest neighbors
• Double Percolation Transition in Superconductor/Ferromagnet Nanocomposites