test Mie code
The Mie code should be tested against a 2nd code and repaired where necessary. The following points need special attention:
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for large grains "wiggles" appear on the absorption and scattering cross section. These may not be real. One example is silicate_1m000.opc.
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when comparing Fig 2b of Li & Draine (2001, ApJ 554, 778) with our calculations, it seemed that the absorption cross section for graphite behaved somewhat differently at long wavelengths. Did we use the exact same refractive indices, or is this a deficiency in the Mie code?
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when going to large grains, the extrapolation of the asymmetry parameter may fail. This can be mitigated by making NMXLIM larger. Is this generally safe? Should we make NMXLIM a parameter of grain size?
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[done] should we switch to an adaptive stepsize integrator to integrate quantities over the size distribution?