DDSCAT.5a9 was released 1998 December 23. It fixes a bug in DDSCAT.5a8,
which resulted in incorrect evaluation of elements of the Mueller scattering
matrix (other than S_11, which was correct) for scattering planes other
than phi=0.

A new version of orient.f was released 1999 March 16. Orientational
averages are now evaluated as described in the UserGuide; prior to this
date averaging over cos(Theta) was evaluated by dividing the range of
cos(Theta) into NTHETA equal intervals, evaluating the scattering
at the midpoint of each interval, and taking the mean. With the new
version of orient.f, Simpson's rule is now used for the quadrature when
an odd value of NTHETA is specified by the user.
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.e5 .
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:

ddscat.par file for m = 1.33+0.01i, N = 4030 dipole tetrahedron, x = 5.

ddscat.par file for m = 1.33+0.01i, N = 13426 dipole tetrahedron, x = 5, 10

ddscat.par file for m = 1.33+0.01i, N = 31598 dipole tetrahedron, x = 5, 10, 15

ddscat.par file for m = 1.33+0.01i, N = 61432 dipole tetrahedron, x = 5, 10, 15

ddscat.par file for m = 1.33+0.01i, N = 105832 dipole tetrahedron, x = 5, 10, 15

m1.33_0.01 refractive index table for m = 1.33+0.01i

ddscat.par file for m = 1.70+0.10i, N = 13426 dipole tetrahedron, x = 5

ddscat.par file for m = 1.70+0.01i, N = 31598 dipole tetrahedron, x = 5, 10

ddscat.par file for m = 1.70+0.10i, N = 61432 dipole tetrahedron, x = 5, 10

ddscat.par file for m = 1.70+0.10i, N = 105832 dipole tetrahedron, x = 5, 10

m1.70_0.10 refractive index table for m = 1.70+0.10i
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.
Back to B.T. Draine's home page.