June 2012      ISSUE 47

PhD position opening

Dr. Daniel Mackowski, with Auburn University, Department of Mechanical Engineering, is taking applications for a PhD student in the area of light scattering. The student should have a background in the mathematical and numerical aspects related to electromagnetic wave scattering by particles. A MS degree in engineering, physics, or a closely related field is required.

This position is limited to US citizens or permanent residents. Pay and benefits are very competitive.

Contact mackodw@auburn.edu for additional information.

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New release of the discrete-dipole approximation scattering code DDSCAT

A new release -- DDSCAT 7.2.2 -- of the discrete-dipole approximation scattering code DDSCAT is now available. This corrects a bug that was present in versions 7.2.0 and 7.2.1 .

The bug fix addressed the following issue:

When NRFLD=1 in ddscat.par AND calculations are done for multiple orientations of the target, or multiple wavelengths, or multiple radii, the calculations for the first wavelength, orientation, and radius (w000r000k000) are correct, but subsequent calculations may be incorrect. The problem occurred because an array was corrupted during the call to subroutine WRITEPOL, due to inconsistency in the ordering of the argument list.

Calculations with NRFLD=0 were NOT affected by this problem.

If you carried out calculations with NRFLD=1 that used multiple wavelengths, orientations, or radii, it is recommended that you repeat the calculations using version 7.2.2 .

We are grateful to Dr. Rodrigo Alcaraz de la Osa for calling this issue to our attention.

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The UserGuide (no changes needed) remains available from http://arxiv.org/abs/1202.3424

The complete DDSCAT 7.2.2 package can be downloaded from http://code.google.com/p/ddscat

The code distribution is ddscat7.2.2_120605.tgz

You can also download the set of "worked examples" that are referred to in the UserGuide: ddscat7.2.2_examples_120605.tgz

Windows executables can be downloaded from http://code.google.com/p/ddscat/wiki/Windows

DDSCAT 7.2 is gratis, subject to the GNU General Public License. [You may copy, distribute, and/or modify the software identified as under this agreement. If you distribute copies of this software, you must give the recipients all the rights that you have.]

As always, please let us know if you encounter problems downloading DDSCAT, or if you have trouble using DDSCAT (but **please** read the manual carefully before reporting problems!!).

Version 7.1 is no longer supported, although it will continue to be available on the google code site. If you have been using Version

7.1 (or an earlier version) please switch to Version 7.2.

We hope that DDSCAT 7.2 will prove useful in your research. If you publish papers using DDSCAT 7.2, please cite

Draine, B.T., & Flatau, P.J. 1994, "Discrete dipole approximation for scattering calculations", JOSA A, 11, 1491-1499

and relevant papers describing the DDA and its implementation in DDSCAT, e.g.,

Goodman, J.J., Draine, B.T., & Flatau, P.J. 1991, "Application of FFT Techniques to the Discrete Dipole Approximation", Optics Letters, 16, 1198-1200

Draine, B.T., & Flatau, P.J. 2008, "Discrete-dipole approximation for periodic targets: theory and tests", JOSA A, 25, 2693-2703

Flatau, P.J., & Draine, B.T. 2012, "Fast near-field calculations in the discrete dipole approximation on regular rectilinear grids", Optics Express, 20, 1247-1252

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New version of ADDA (1.1) has been released.

The most important changes are:

New OpenCL-based version of ADDA to effectively use GPUs for simulations.

Calculation of radiation forces was largely improved.

Three new miscellaneous packages: 'hyperfun' (contributed by Josef Gasteiger), 'pip' (contributed by Roman Schuh and Thomas Wriedt), and 'parse_log'. In particular, it greatly simplifies using many common 3D shape formats together with ADDA.

ADDA executables for 64-bit Windows are now available. For a more detailed list please see http://code.google.com/p/a-dda/wiki/ReleaseNotes.

You are advised to upgrade to a new version, which can be downloaded (both main package and, if needed, executables for Windows) from: http://code.google.com/p/a-dda/downloads/

For a full announcement please see - http://groups.google.com/group/adda-announce/t/48b638e9ee48748a