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The Discrete Dipole Approximation for Scattering and Absorption of Light by Irregular Particles

DDSCAT, a Fortran code for calculating scattering and absorption of light by irregular particles, has been jointly developed by Bruce T. Draine (Dept. of Astrophysical Sciences, Princeton University) and Piotr J. Flatau (Scripps Institution of Oceanography, UCSD); the current version is DDSCAT.6.0 . This code is publicly available (see below). If you choose to use it, please send email to <draine@astro.princeton.edu> "registering" as a user; registered users of DDSCAT will be notified when updates to the code are made.

User Guide for DDSCAT.6.0

An extensive User Guide is available: "User Guide to the Discrete Dipole Approximation Code DDSCAT.6.0", by B.T. Draine and Piotr J. Flatau. A copy of this document (postscript or pdf) can be obtained from astro-ph/0309069 and can be cited as The following files are of interest:

Downloading the DDSCAT Code

Unix users will find it most convenient to download Non-unix users can use anonymous ftp to download the code (*.FOR files), documentation (UserGuide.ps), and sample parameter files (ddscat.par and diel.tab).

History of recent releases:

Benchmark Calculations

Draine (2000) has published benchmark calculations for scattering by tetrahedral targets. Two target refractive indices have been considered: m=1.33+0.01i and m=1.70+0.10i . Scattering was calculated for one target orientation and two incident polarizations. In each case solutions were iterated until the DDA equations were satisfied with a fractional error < 1.e-5 . CPU times are reported below for a 600 MHz Pentium III system running Red Hat Linux 6.2, using the Portland Group pgf77 compiler.

CPU time (s) on 600 MHz Pentium III System

m=1.33+0.01i tetrahedron

N x=5 x=10 x=15
4030 31. -- --
13426 141. 267. --
31598 356. 639. 1106.
61432 792. 1480. 2476.
105832 1298. 2292. 4226.
m=1.7+0.1i tetrahedron
N x=5 x=10
13426 377. --
31598 939. 2104.
61432 2115. 4429.
105832 3585. 7335.

For users wishing to repeat one or more of these calculations using DDSCAT.5a10 (which may be useful to reassure you that DDSCAT.5a10 is working properly on your computer), sample ddscat.par files are available for downloading:

Please consult the DDSCAT UserGuide (see above) for an explanation of the parameters in the ddscat.par file.

For additional information on other techniques for numerical calculation of electromagnetic scattering by finite targets, see also the SCATTERLIB library of light scattering codes maintained by Piotr Flatau.

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