Tuning the dielectric response in a nanocomposite material through nanoparticle morphology

Abstract

Dielectric response of nanocomposites with metal-nanoparticle inclusions can be enhanced significantly by changing nanoparticle shape and size, even without ramping up volume loading of inclusions.

Dielectric metal/metal oxide nanocomposites: modeling response properties at multiple scales

“…This suggests one option, which is to consider the percent atomic loading as a stand-in for volume loading. [23,24] While this is a sufficient definition when loading is used only as a system descriptor, we find that a more rigorous definition of volume is necessary when developing inclusion shape, size and loading parameters for FEM.…”

“…This results in stronger polarization within a shell of matrix ions. [23,24] There are two contributors to this effect: The local field enhancement due to the polarization of the inclusion, and the higher polarizability of the interfacial matrix layer, because of matrix electronic structure changes due to its interactions with the polarized particles. In Ag 8 /MgO, particle -O anion electron coupling leads to the spreading of O-sp 3 orbitals for a shell approximately 3 Å thick.…”

“…[23] For larger anisotropic inclusions, the polarization enhancement was found to be mostly localized within the two layers of Mg/O ions closest to the inclusion. [24] To capture coupling for a FEM model, we include an interfacial layer, assigned a permittivity by fitting the continuum model to quantum dynamics results. where…”

“…However, these methods scale poorly with the number of electrons, meaning they can only be applied to composites where the inclusions are sufficiently small to allow a unit cell on the order of a few hundred atoms. In two earlier publications from our group, [23,24] Car-Parrinello quantum mechanical molecular dynamics (quantum dynamics) simulations were used to study nanocomposite dielectrics by optimizing electronic and nuclear coordinates under an applied electric field.…”

“…In nanostructured systems, quantum effects due to small feature size and the electronic coupling between the inclusion and matrix can dominate the polarization response of the material. [23,24] Although not directly addressing quantum effects, the FEM can be parametrized for these interactions as well as the shape effects that become important for non-trivial loading.…”