Wulff-Based Approach to Modeling the Plasmonic Response of Single Crystal, Twinned, and Core–Shell Nanoparticles

The growing interest
in plasmonic nanoparticles and their increasingly
diverse applications is fuelled by the ability to tune properties
via shape control, promoting intense experimental and theoretical
research. Such shapes are dominated by geometries that can be described
by the kinetic Wulff construction such as octahedra, thin triangular
platelets, bipyramids, and decahedra, to name a few. Shape is critical
in dictating the optical properties of these nanoparticles, in particular
their localized surface plasmon resonance behavior, which can be modeled
numerically. One challenge of the various available computational
techniques is the representation of the nanoparticle shape. Specifically,
in the discrete dipole approximation, a particle is represented by
discretizing space via an array of uniformly distributed points-dipoles;
this can be difficult to construct for complex shapes including those
with multiple crystallographic facets, twins, and core–shell
particles. Here, we describe a standalone user-friendly graphical
user interface (GUI) that uses both kinetic and thermodynamic Wulff
constructions to generate a dipole array for complex shapes, as well
as the necessary input files for DDSCAT-based numerical approaches.
Examples of the use of this GUI are described through three case studies
spanning different shapes, compositions, and shell thicknesses. Key
advances offered by this approach, in addition to simplicity, are
the ability to create crystallographically correct structures and
the addition of a conformal shell on complex shapes.