84 research outputs found
Accelerating iterative solvers in the discrete dipole approximation using dedicated initial guesses
No full textInternational audienceThe Discrete Dipole Approximation (DDA) [1] is a versatile and widely used method for simulatinglight scattering by particles with arbitrarily shapes and internal structure, ranging in sizes from muchsmaller than to several tenths of a wavelength. Its flexibility, coupled with open-source implementationslike ADDA, DDSCAT, and IF-DDA, has enabled applications in biology, nanotechnology, and climatestudies. However, the high computational cost of solving the underlying large-scale linear systemsremains a significant limitation.This work focuses on accelerating the iterative solvers within the DDA by improving their initializationstrategies. Previous works on DDA implementations, have explored preconditioning, block iterativemethods, and initial guesses to enhance efficiency. While these approaches have yielded modest gains,achieving acceleration factors of 2–3 for block methods and up to 50% improvement for initial guesses,they leave significant room for enhancement. We aim to optimize initial guesses to improve solverconvergence, particularly for soft particles.We build on existing studies [2,3] that demonstrated promising results using scalar solutions orapproximate methods as initial guesses and compared several iterative solver methods. Our approachaims to extend these strategies by incorporating multiple approximations, theory, and geometric optics.For specific particle shapes, such as spheres and spheroids with refractive indices and sizes consistentwith previous study [4], these advanced approximations are expected to yield substantial improvements.We also plan to benchmark these advanced initial guess strategies by directly integrating initialguesses produced by IF-DDA [2,3], such as scalar fields (e.g., uGu), into the iterative solvers available inADDA. This approach will allow us to compare the performance of iterative methods across both codes,providing a comprehensive evaluation of their efficiency under different configurations. Additionally, byexploring the interoperability between ADDA and IF-DDA, we aim to bridge their formulations,contributing to open-source development and fostering broader adoption within the DDA community.Our results aim to provide a comparative analysis of initial guesses used with already establishedoptimized iterative solvers, highlighting scenarios where these advanced strategies significantly reducecomputational costs. Furthermore, initial guesses can be combined with preconditioning techniques andblock iterative methods to enhance solver performance. These approaches are also extendable toparticles with more complex geometries, broadening the applicability of our methods across diversescattering problems. By refining solver initialization, this study paves the way for more efficient DDAsimulations across diverse applications.[1] Purcell, E. M. and Pennypacker, C. R., Astrophys. J., 186, p. 705, 1973.[2] Chaumet, P. C., J. Quant. Spectrosc. Radiat. Transfer, 312, 108816, 2024.[3] Chaumet, P. C., Maire, G., and Sentenac, A., J. Quant. Spectrosc. Radiat. Transfer, 298, 108505, 2023.[4] Inzhevatkin, K. G. and Yurkin, M. A., J. Quant. Spectrosc. Radiat. Transfer, 277, 107965, 2022
Response to Comment Paper by Dr. Maxim A. Yurkin for 2021 JGR Paper “Evaluation of Higher‐Order Quadrature Schemes in Improving Computational Efficiency for Orientation‐Averaged Single‐Scattering Properties of Nonspherical Ice Particles”
No full textInternational audienceAbstract We thank Dr. Yurkin for his considered and constructive critique of our paper. We respond to his insightful comments below and hope that this discussion motivates further communication and cooperation and benefits to the scattering by small particles community
Recent developments of the ADDA code
No full textInternational audienceThe open-source code ADDA (https://github.com/adda-team/adda) is based on the discrete dipoleapproximation (DDA) – a numerically exact method derived from the frequency-domain volume-integralformulation of Maxwell’s equations [1]. It can simulate the interaction of electromagnetic fields(scattering and absorption) with finite 3D objects of arbitrary shape and composition. Besides standardsequential execution on a single CPU or GPU, ADDA can run on a multiprocessor distributed-memorysystem, parallelizing a single DDA calculation. This, combined with the almost linear scaling ofcomputational complexity with the number of dipoles (discretization voxels), allows large system sizesand/or fine discretization levels.ADDA is written in C99 and is highly portable. It provides full control over the scattering geometry(particle morphology and orientation, incident beam) and allows users to calculate a wide variety ofintegral and angle-resolved quantities. In addition to far-field scattering by various beams (includingbuilt-in Gaussian and Bessel beams), this includes near fields as well as excitation by a point dipole or afast electron. Moreover, ADDA can rigorously and efficiently simulate the scattering by particles near aplane homogeneous substrate or embedded in a homogeneous absorbing host medium. It alsoincorporates many DDA improvements aimed at increasing both accuracy and computational speed.In this talk we will focus on the recently implemented ADDA features, either incorporated into themain codebase or available in separate development branches. These include a wide range of built-inBessel beams [2] and simulations of electron energy-loss spectroscopy (EELS) and cathodoluminescence[3]. The latter two can be computed in an arbitrary passive host medium, even when the electron emitsthe Cherenkov radiation, or for particles on top of a semi-infinite substrate (under certainapproximations). These capabilities also generalize the concept of the Purcell factor (i.e., theenhancement of a point-dipole emitter), which ADDA can rigorously compute in free space or near asubstrate [4].Next, we will discuss the analytical approximations of Green’s-tensor integrals for the correspondingDDA formulation, known as IGT, as well as various enhancements to the iterative solvers. Theseenhancements include block- or shifted iterative methods to accelerate computations for multipleincident beams (e.g., particle orientations) or refractive indices, as well as the use of specialized initialguesses for large particles [5]. Finally, many of these features are accessible through a graphical userinterface and we are actively working on integrating ADDA with Spack – a package manager thatfacilitates installation on a wide range of systems, including supercomputing environments.[1] M. A. Yurkin and A. G. Hoekstra, J. Quant. Spectrosc. Radiat. Transfer 112, 2234 (2011).[2] S. A. Glukhova and M. A. Yurkin, Phys. Rev. A 106, 033508 (2022).[3] A. A. Kichigin and M. A. Yurkin, J. Phys. Chem. C 127, 4154 (2023).[4] A. E. Moskalensky and M. A. Yurkin, Phys. Rev. A 99, 053824 (2019).[5] K. G. Inzhevatkin and M. A. Yurkin, J. Quant. Spectrosc. Radiat. Transfer 277, 107965 (2022)
How a phase image of a cell with nucleus refractive index smaller than that of the cytoplasm should look like?
No full textMicrowave scattering by rough polyhedral particles on a surface
No full textInternational audienceThe electromagnetic (EM) scattering by non-symmetric wavelength-scale particles on a planar surface has numerous applications in the remote sensing of planetary bodies, both in planetary and geo-sciences. We conduct numerical simulations of EM scattering by rough polyhedral particles (with 12 or 20 faces) using the discrete-dipole approximation and contrast the results to that of spheres. The particles have permittivities corresponding to common minerals in the microwave regime (ϵr=4.7+0.016i and 7.8+0.09i), and a size-frequency distribution (SFD) consistent with the observed scattering properties (power-law distribution of size parameters between 0.5 and 8 with an index from −2.5 to −3.5). The assumed substrate permittivity 2.4+0.012i corresponds to a powdered regolith. We present what roles the particle roundness, permittivity, and SFD for a realistic range of parameters play in the EM scattering properties as a function of incidence angle with a focus on backscattering in microwave-remote-sensing applications. The particle roundness and SFD have a clearly observable effect on the polarimetric properties, while the role of permittivity is relatively minor (in the studied range). Among various backscattering observables, the circular polarization ratio is the least sensitive to the decrease of the upper boundary (down to a size parameter of 3) and the index of the SFD
Capabilities of the ADDA code for nanophotonics
No full textInternational audienceThe open-source code ADDA (https://github.com/adda-team/adda) is based on the discrete dipole approximation (DDA) – a numerically exact method derived from the frequency-domain volume-integral formulation of the Maxwell equations [1]. It can simulate interaction of electromagnetic fields (scattering and absorption) with finite 3D objects of arbitrary shape and composition. Besides standard sequential execution on a CPU or a GPU, ADDA can run on a multiprocessor distributed-memory system, parallelizing a single DDA calculation. This together with almost linear scaling of computational complexity with the number of dipoles (discretization voxels) allows huge system sizes and/or fine discretization levels. The code is written in C99, is highly portable, and includes a graphical user interface.ADDA provides full control over the scattering geometry (particle morphology and orientation, incident beam) and allows one to calculate a wide variety of integral and angle-resolved quantities. In addition to far-field scattering by various beams (including built-in Gaussian and Bessel ones), this includes near fields as well as excitation by a point dipole or a fast electron. Moreover, ADDA can rigorously and efficiently simulate the scattering by particles near a plane homogeneous substrate or placed in a homogeneous absorbing host medium. It also incorporates many DDA improvements aimed at increasing both the accuracy and computational speed.At the conference we will describe the main features of ADDA, including the ones still in development, with special emphasis on nanoparticles. They include a wide range of built-in Bessel beams [2] and simulations of electron energy-loss spectroscopy (EELS) and cathodoluminescence [3]. The latter two can be computed in an arbitrary passive host medium, even when the electron emits the Cherenkov radiation, or for particles on top of a semi-infinite substrate (under certain approximations). These capabilities also generalize the concept of the Purcell effect, which ADDA can rigorously compute in free space or near a substrate. Placing a point source inside a nanoparticle allows one to calculate near-field radiative heat transfer or Casimir forces between two objects. Recent numerical improvements include block- or shifted iterative methods to accelerate computations for multiple incident beams (e.g., particle orientations) or refractive indices.References:[1] M.A. Yurkin and A.G. Hoekstra, “The discrete-dipole-approximation code ADDA: Capabilities and known limitations,” J. Quant. Spectrosc. Radiat. Transfer 112, 2234–2247 (2011).[2] S.A. Glukhova and M.A. Yurkin, “Vector Bessel beams: General classification and scattering simulations,” Phys. Rev. A 106, 033508 (2022).[3] A.A. Kichigin and M.A. Yurkin, “Simulating electron energy-loss spectroscopy and cathodoluminescence for particles in arbitrary host medium using the discrete dipole approximation,” J. Phys. Chem. C 127, 4154–4167 (2023)
Beyond the Lorenz-Mie theory: Simulating light-scattering by arbitrary particles with the discrete dipole approximation
No full textInternational audienceInteraction of light with particles is a central concept in applications ranging from remote sensing of aerosols or interstellar dust to advanced imaging techniques and various molecular sensing involving nanoparticles. Corresponding simulations are not trivial for particles of complex shape and internal structure, while the discrete dipole approximation (DDA) is one of the versatile methods to handle such problems. The DDA has a simple underlying physical picture and, at the same time, is a numerically exact method – a special case of volume-discretization method of moments. Notably, the DDA is applicable to almost any electromagnetic problem involving non-magnetic particles. It can handle arbitrary shaped beams, particles in complex environments (e.g., on a multi-layered substrate), and simulate a broad range of quasi-classical electromagnetic phenomena (such as emission enhancement, near-field radiative heat transfer, and electron energy-loss spectroscopy). I will also discuss computational aspects and modern DDA formulations. The latter are implemented in open-source DDA codes, such as ADDA, which largely explains the method’s popularity. Finally, I will highlight current capabilities and limitations (open questions) of the DDA
The discrete dipole approximation for scattering simulations of subwavelength particles
No full textInternational audienceElectromagnetic scattering is widely used in remote sensing of various objects ranging from metal nanoparticles and macromolecules to atmospheric aerosols and interstellar dust. All these applications require accurate simulations, which are not trivial for particles of arbitrary shape and internal structure. The discrete dipole approximation (DDA) is one of the versatile methods to handle such problems.This talk will begin with an introduction to the DDA, covering both the basic underlying physical picture and a rigorous derivation starting from the integral form of Maxwell’s equation for the electric field. This derivation emphasizes that the DDA is a numerically exact method and a special case of volume-discretization method of moments. Notably, the DDA is applicable to almost any electromagnetic problem involving non-magnetic particles. It can handle arbitrary shaped beams, particles in complex environments (e.g., on a multi-layered substrate), and simulate a broad range of quasi-classical electromagnetic phenomena (such as emission enhancement, near-field radiative heat transfer, and electron energy-loss spectroscopy).Although the DDA applies to a wide range of particle sizes, the talk will focus specifically on subwavelength ones, discussing the corresponding computational aspects and modern DDA formulations. The latter are implemented in open-source DDA codes, such as ADDA, which largely explains the method’s popularity. Finally, I will highlight current capabilities and limitations (open questions) of the DDA in application to subwavelength systems
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