Plasmonx: Open-Source Code Simulates Nanoplasmonic Response of Complex Structures with Frequency-Dependent Fluctuating Charges

Understanding how light interacts with nanoscale materials is crucial for advances in fields ranging from sensing and imaging to catalysis and data storage, yet simulating these interactions accurately can be computationally demanding. Tommaso Giovannini from University of Rome Tor Vergata, Pablo Grobas Illobre, Piero Lafiosca, and colleagues at Scuola Normale Superiore now present plasmonX, a new open-source code designed to overcome these challenges. This freely available software allows researchers to model the optical response of complex nanostructures using both detailed atomistic descriptions and more computationally efficient implicit methods, offering a versatile toolkit for investigating plasmonic phenomena and accelerating innovation in nanophotonics. The code’s ability to handle a wide range of materials and geometries, combined with its post-processing capabilities for analysing electric fields and charge distributions, represents a significant step forward in computational nanoplasmonics.

This innovative approach combines quantum mechanical calculations with classical electromagnetism, achieving a balance between accuracy and computational efficiency. The framework is particularly well-suited for studying metallic alloys and complex nanostructures where composition and atomic arrangement significantly influence optical behaviour. The framework incorporates tools for generating and manipulating complex nanostructure geometries and is optimized for performance through parallel computing, utilizing multi-core processors and potentially graphics processing units.

It also employs the Fast Multipole Method, an algorithm that reduces computational demands, and leverages Intel’s Math Kernel Library for optimized mathematical operations. Built with C++ and modern software engineering practices, plasmonX is designed for cross-platform compatibility and benefits from extensive documentation and a collaborative community through a GitHub repository. plasmonX excels at modelling alloy and core-shell nanoparticles, accurately predicting their optical properties and simulating Surface-Enhanced Raman Scattering, a phenomenon used to study molecular vibrations on plasmonic surfaces. It also models colloidal nanoparticles and their interactions with light, studies time-dependent phenomena in plasmonics, and combines atomistic simulations with electromagnetic modelling to understand light-matter interactions at the molecular level. This combination of accuracy, versatility, efficiency, and open-source development makes plasmonX a powerful tool for advancing the field of plasmonics.

PlasmonX Code Simulates Nanostructure Optical Response

Scientists have created plasmonX, a new open-source code designed to simulate how light interacts with complex nanostructures, addressing a long-standing challenge in nanophotonics. The code overcomes limitations in existing methods by offering a versatile platform that supports both detailed atomistic descriptions and simplified representations of nanomaterials, allowing researchers to model a wider range of structures with greater accuracy. This innovation enables detailed investigation of light confinement at the nanoscale, with potential applications in spectroscopy, sensing, quantum optics, and nanoelectronics. To accurately model these nanostructures, the team implemented frequency-dependent fluctuating charges and dipoles models, which describe the response properties of atomistic structures composed of simple and d-metals, graphene, and multi-metal combinations.

These models account for the physical mechanisms underlying the optical response, offering accuracy comparable to advanced quantum mechanical techniques while remaining computationally efficient. The researchers also incorporated the Boundary Element Method, implemented in both the dielectric polarizable continuum model and integral equation formalism variants, to provide implicit, non-atomistic modelling capabilities. The code’s versatility extends to its post-processing module, which enables detailed analysis of electric field-induced properties, such as charge density and electric field patterns, providing a comprehensive understanding of the nanostructure’s behaviour. Rigorous testing using gfortran and Intel’s Math Kernel Library ensures robust and reliable performance. This innovative approach bridges the gap between quantum accuracy and classical scalability, allowing for the simulation of realistic nanostructures with a high degree of precision and offering a powerful tool for researchers in the field.

PlasmonX Simulates Nanoparticle Optical Properties Accurately

Scientists have developed plasmonX, a new open-source code designed to simulate how light interacts with complex nanostructures. The code offers a versatile platform capable of modelling materials at both the atomic level and through simplified representations, providing flexibility for a wide range of investigations. It employs two primary methods: frequency-dependent fluctuating charges and dipoles for atomistic structures, and the Boundary Element Method for implicit representations, allowing researchers to accurately describe the optical properties of nanomaterials. To demonstrate the code’s capabilities, the team investigated ten silver-gold alloy nanoparticles, each with a diameter of 3.

5nm and varying gold content from 0% to 100%. Calculations revealed a linear relationship between the percentage of gold and the plasmon resonance frequency, closely matching experimental observations and confirming Vegard’s law. The intensity of the plasmon band was also found to decrease exponentially with increasing gold concentration, aligning with existing experimental findings. These results demonstrate the code’s ability to accurately predict the optical behaviour of alloy nanoparticles. Further analysis focused on a gold dimer with a 5 Å gap, revealing a strong plasmon peak at 2.

28 eV. Using plasmonX, scientists calculated the induced density and electric field at this peak, demonstrating the formation of a boundary dipolar plasmon, characterized by a highly localized hot spot in the gap between the two gold structures. The team generated 2D maps of the electric field using a Python script integrated with plasmonX, confirming intense field enhancement within the gap, consistent with ab initio calculations. The work highlights the code’s capacity to model complex electromagnetic phenomena at the nanoscale and provides a valuable tool for researchers studying plasmonics and nanophotonics.

PlasmonX, A Versatile Nanostructure Simulation Code

This work presents plasmonX, a new open-source code designed to simulate the behaviour of light interacting with nanostructures, offering a versatile platform for researchers in the field. The code uniquely combines both atomistic and continuum electrodynamic models, allowing for detailed simulations of a wide range of materials and structures, from simple metals to complex multi-metal arrangements. By implementing fluctuating charge and dipole models alongside boundary element methods, plasmonX accurately calculates the optical response of these nanostructures, even those containing millions of atoms. The researchers demonstrate the code’s capabilities through simulations that reproduce established results for specific systems, validating its accuracy and reliability.

The modular design and efficient numerical solvers within plasmonX enable scalable simulations, representing a significant advancement in computational plasmonics. The simulation data used in the study are available to support further research and verification. Acknowledging current limitations, the authors outline future development plans, including extending the code to simulate ultrafast phenomena and modelling nanostructures within complex environments. Further work will focus on combining atomistic and continuum approaches to reduce computational cost and implementing fast multipole algorithms to enhance scalability for even larger systems.