Bruce T. Draine
Princeton University Observatory
Princeton NJ 08544-1001
(draine@astro.princeton.edu)
and
Piotr J. Flatau
University of California, San Diego
Scripps Institution of Oceanography
La Jolla CA 92093-0221
(pflatau@ucsd.edu)
last revised: 2000 June 12
DDSCAT.5a is a freely available
software package which applies the
``discrete dipole approximation'' (DDA) to calculate scattering
and absorption of electromagnetic waves by targets with arbitrary
geometries and complex refractive index. The DDA approximates
the target by an array of polarizable points.
DDSCAT.5a requires that these polarizable points be located
on a cubic lattice. DDSCAT.5a10 allows
accurate calculations of electromagnetic scattering from targets
with ``size parameters'' 
provided the
refractive index m is not large compared to unity (|m-1| < 1).
The DDSCAT package is written in Fortran and is highly portable. The program supports calculations for a variety of target geometries (e.g., ellipsoids, regular tetrahedra, rectangular solids, finite cylinders, hexagonal prisms, etc.). Target materials may be both inhomogeneous and anisotropic. It is straightforward for the user to ``import'' arbitrary target geometries into the code, and relatively straightforward to add new target generation capability to the package. DDSCAT automatically calculates total cross sections for absorption and scattering and selected elements of the Mueller scattering intensity matrix for specified orientation of the target relative to the incident wave, and for specified scattering directions.
This User Guide explains how to use DDSCAT.5a10 to carry out electromagnetic scattering calculations. CPU and memory requirements are described.
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