A recursive cell multipole method for atomistic electrodynamics models.

Area of Science:

• Computational electromagnetics
• Plasmonics
• Nanophotonics

Background:

• Retardation effects are crucial for large plasmonic nanoparticles but computationally expensive.
• Existing models often neglect these effects due to high computational costs in atomistic electrodynamics.

Purpose of the Study:

• To develop and implement a computationally efficient method for including retardation effects.
• To enable accurate optical property calculations for large atomistic plasmonic nanoparticles.

Main Methods:

• Derivation and implementation of a recursive fast multipole method (FMM) in Cartesian coordinates.
• Recursive calculation of higher-order electrodynamic interaction tensors for reduced complexity.
• Application to large plasmonic nanoparticles (over a million atoms), focusing on nanorods and dimers.

Main Results:

• The developed FMM method successfully incorporates retardation effects with controlled accuracy.
• Fifth-order expansion offers a balance between accuracy and computational time.
• Demonstrated analysis of retardation's impact on near- and far-field properties of nanorods and dimers.

Conclusions:

• The recursive FMM provides a viable solution for simulating large plasmonic systems with retardation.
• This method facilitates the study of field confinement in nanorod junctions.
• Potential applications include simulations requiring precise near-field properties, like surface-enhanced Raman scattering.