SCATTERLIB Light Scattering Codes Library

Introduction

SCATTERLIB  is a collection of light scattering codes. Emphasis is on access to source codes. Possible applications include: atmospheric and oceanic radiative transfer, ocean color, flow cytometry, particle sizing, paints, light scattering by non-spherical and spherical particles, radar backscatter. This library is dated now.

Last corrections: November 2005

Coated spheres

Here is a collection of light scattering codes for spheres and concentric spheres.

Multispheres

Light scattering on Spheroids (modal and T-matrix)

Here is a collection of light scattering codes on spheroids. It is possible to attack the problem using separation of variables ("Mie"-type analysis), or using other techniques such as T-matrix - for homogeneous or "concentric" distribution of refractive index; or volume methods such as discrete dipole approximation (for medium size parameters).

• The code originated for the study described in Rogers and Martin, 1979. Latter, many subroutines to treat the case of complex refractive indices have been added
  ftp://ftp.cita.utoronto.ca/cita/pgmartin/spheroid
• Voshchinnikov SPH16h Calculates Light Scattering by Spheroidal Particles (extinction, scattering and absorption efficiency factors for prolate or oblate homogeneous spheroids).
• See also home page of Mischenko

I think this section is getting obolete. There may be more codes available but I did not follow last several years development (2005). Home page of Thomas Wriedt may have more information.

Light scattering on infinite cylinders.

Here is a collection of light scattering codes for the case of infinite cylinder.

Slab scattering

Here is a collection of scattering codes for slabs.

• Barber and Hill slab code. A computer program from the text, Light Scattering by Particles: Computational Methods by P.W. Barber and S.C. Hill, may be used to calculate the reflected, transmitted, and internal intensities for a finite-thickness slab illuminated by a plane wave incident perpendicular to the surface.

Discrete Dipole Approximation

In the discrete dipole approximation the target is replaced by an array of point dipoles; the electromagnetic scattering problem for the array of point dipoles is then solved essentially exactly. This method is also called method of momets, coupled dipole approximation, digitized Green's function. These codes work for 3D problems up to size parameter x=10-20 (x=2pi r/lambda). The method compares well with scattering efficiencies for spheres (with Mie solution). Review paper by Draine and Flatau (Applied Optics, 1994) is related to DDSCA (see also references to this paper (on "google scholar" of "web of science").  There are also some important new developments in the last 5 years (2000-2005): (a) work by Mackowski to derive analytical orientational averaging using T-matrix approach in DDA approximation; (b) calculation of periodic structures (i.e. of inifinite extend) using variant of DDA; (c) extensions to calculate particles placed on surfaces.

DDA - List of Solvers

T-matrix.

Here is a collection of "T-matrix" scattering codes.

• Barber and Hill codes. Nine computer programs from the text, Light Scattering by Particles: Computational Methods by P.W. Barber and S.C. Hill, may be used to calculate the light scattered by nonspherical particles using the T-matrix method. An auxiliary program determines array dimensions for the nine basic programs.
  1. T1.for convergence test and store [T] matrix
  2. T2.for scattering for fixed orientation - use [T] matrix
  3. T3.for scattering in all directions for a particle in fixed orientation - use [T] matrix
  4. T4.for scattering for 2D random orientation - use [T] matrix
  5. T5.for scattering for 3D random orientation - use [T] matrix
  6. T6.for scattering matrix calculations - use [T] matrix
  7. T7.for scattering efficiency vs size parameter
  8. T8.for internal intensity distribution - 2D and 3D - use [A] matrix
  9. T9.for external intensity distribution - 2D and 3D - use [T] matrix
  10. dim.for obtain nrank-dependent array dimensions for all programs

The codes of Mackowski and Mishchenko are popular these days (circa 2005). See Mishchenko's home page. Also look at home page of Thomas Wriedt.

Anomalous diffraction approximation

Anomalous diffraction approximation, van de Hulst approximation, eikonal approximation, high energy approximation, soft particle approximation.

Anomalous diffraction approximation (ADT) offers very approximate but computationally fast technique to calculate extinction, scattering, and absorption efficiencies. It agrees well with the "Mie" (modal) calculations for spheres, cylinders, spheroids, and coated spheres. Absolute value of refractive index has to be close to 1, and size parameter should be large. However, semi-empirical extensions to small size parameter, and larger refractive index are possible. It is NOT possible to calculate full range of phase function or asymmetry parameter - g in this approximation. The main advantage of the ADT is that one can (a) Calculate, in closed form, extinction, scattering, and absorption efficiencies for many typical size distributions; (b) Find solution to the inverse problem of predicting size distribution from light scattering experiments (several wavelengths); (c) For parameterization purposes of single scattering (inherent) optical properties in radiative transfer codes. One older review is Mahood, Robert W. "The application of vector diffraction to the scalar anomalous diffraction approximation of van de Hulst", 1987, Thesis (M.S.)--Pennsylvania State University. In recent years (circa 2005) more ADT papers were published, particlly because the calculations are very simple. But, more importantly there are now papers which compare ADT with exact methods for non-spherical particles - inevitable development, considering that ADT is very approximate.

• ADSCAT code This code is from my (Flatau) Ph.D. and is getting obsolete now. I wrote it in 1992. There are many papers describing ADT extensions. ADSCAT is a FORTRAN program to calculate scattering and absorption of electromagnetic radiation by arbitary convex polyhedron target using the "Anomalous Diffraction Theory" (ADT). The target is represented by an array of vertices; the matrix of distances inside the target is generated as a first step (TRACE) which is followed by the ADT calculations (ADSCAT). The ADT was apparently first proposed by van de Hulst.
• Spheres. Basic ADT for sphere is just several lines of code. It is amazing that these expressions can be analytically integrated for several size distributions.

Related sites

Probably the best site which is direct competitor to this one (and much more comprehensive I may add)
A list of electromagnetic scattering programmes supported by Thomas Wriedt

Other sites (but there must be many more now)

• Applied Computational Electromagnetics Society
• Numerical Electromagnetics Modelling Codes
• EMLIB is a WEB site for the free distribution of electromagnetics (EM) software and related information.
• V. Ossenkopf (Effective media calculator, Kramers-Kronig analysis , Mie scattering program)
• T-matrix Codes (Michael I. Mishchenko)

Related numerical methods

Conjugate gradient methods. This technique to solve linear system of complex equations is often employed together with the discrete dipole approximation or method of moments. When coupled with FFT to solve the convolution problem it is called CG-FFT. In the DDSCAT code we use excellent package by Rudnei Dias da Cunha and Tim Hopkins.

1. The Parallel Iterative Methods (PIM) by Rudnei Dias da Cunha (rdd@ukc.ac.uk) and Tim Hopkins (trh@ukc.ac.uk) is a collection of Fortran 77 routines designed to solve systems of linear equations (SLEs) on parallel computers using a variety of iterative methods.
2. Complex and real conjugate gradient package by Flatau, Evans, and Schneider.
3. Templates for the Solution of Linear Systems: Building Blocks for Iterative Methods. See also NETLIB for the source code of templates.
4. Conjugate Gradient Method Without Agonizing Pain by Jonathan R. Shewchuk [PostScript].
5. Mathematical Optimization textbook.