Finite Element Modeling of the Dielectric Response of Metal/Metal Oxide Nanocomposites: Coarse-Graining the Quantum Response

Abstract

Nanocomposite materials with metallic or ceramic inclusions show great promise as highly-tunable functional materials, particularly for applications where high dielectric permittivities are desirable, such as charge-storage or energy-storage materials. These applications present a challenge for computational approaches, as the field response of the nanoscale inclusion is quantum in nature, yet any representative sample of the material must encompass hundreds if not thousands of atoms. As currently implemented, finite element methods offer some predictive power for macroscale matrix-inclusion composites. However, their applicability cannot necessarily be extended to few-nanometer, molecular scale inclusions, where quantum and interfacial effects gain importance in the overall response to the applied field. Here, we develop an adjustable finite element method approach to calculate the low frequency dielectric constant of composites consisting of a metal-oxide matrix with molecular-scale silver inclusions, by introducing an interfacial layer in the general model. A process for coarse-graining atomistic ab initio results to generate best fit finite element models is also laid out in this work. We show that a continuum model informed by ab initio results can capture many of the relevant polarization effects in a metal/metal oxide nanocomposite, at a fraction of the computational cost.