  We explore whether assumptions about dust grain shape affect resulting
estimates of the composition and grain size distribution of the AU Microscopii
(AU Mic) debris disk from scattered light data collected by Lomax et al.
(2018). The near edge-on orientation of the AU Mic debris disk makes it ideal
for studying the effect of the scattering phase function (SPF) on the measured
flux ratios as a function of wavelength and projected distance. Previous
efforts to model the AU Mic debris disk have invoked a variety of dust grain
compositions and explored the effect of porosity, but did not undertake a
systematic effort to explore a full range of size distributions and
compositions to understand possible degeneracies in fitting the data. The
degree to which modelling dust grains with more realistic shapes compounds
these degeneracies has also not previously been explored. We find differences
in the grain properties retrieved depending on the grain shape model used. We
also present here our calculations of porous grains of size parameters x = 0.1
to 48 and complex refractive indices (m = n+ik) ranging from n = 1.1 to 2.43
and k = 0 to 1.0, covering multiple compositions at visible and near infrared
wavelengths such as ice, silicates, amorphous carbon, and tholins.
