Multiscaling for Systems with a Broad Continuum of Characteristic Lengths and Times: Structural Transitions in Nanocomposites

TL;DR

This paper develops a multiscale theoretical framework for systems with a broad spectrum of characteristic lengths and times, enabling analysis of complex structural transitions in nanocomposites and similar materials.

Contribution

It introduces a continuous scaling approach using uncountable sets of time variables and order parameters, extending traditional multiscale methods to systems with broad spectra.

Findings

Derived a functional-differential Smoluchowski equation for continuum OP dynamics

Formulated non-local Langevin equations for order parameters

Applied the theory to analyze structural transitions in nanocomposites

Abstract

The multiscale approach to N-body systems is generalized to address the broad continuum of long time and length scales associated with collective behaviors. A technique is developed based on the concept of an uncountable set of time variables and of order parameters (OPs) specifying major features of the system. We adopt this perspective as a natural extension of the commonly used discrete set of timescales and OPs which is practical when only a few, widely-separated scales exist. The existence of a gap in the spectrum of timescales for such a system (under quasiequilibrium conditions) is used to introduce a continuous scaling and perform a multiscale analysis of the Liouville equation. A functional-differential Smoluchowski equation is derived for the stochastic dynamics of the continuum of Fourier component order parameters. A continuum of spatially non-local Langevin equations for the OPs is also derived. The theory is demonstrated via the analysis of structural transitions in a composite material, as occurs for viral capsids and molecular circuits.