  We study how shape affects multiexciton generation (MEG) rates in a
semiconducting nanocrystal by considering CdSe nanorods with varying diameters
and aspect ratios. The calculations employ an atomistic semiempirical
pseudopotential model combined with an efficacious stochastic approach applied
to systems containing up to 20,000 atoms. The effect of nanorod diameter and
aspect ratio on multiexciton generation rates is analyzed in terms of the
scaling of the density of trion states and the scaling of the Coulomb
couplings. Both show distinct scaling from spherical nanocrystals leading to a
surprising result where the multiexciton generation rates are roughly
independent of the nanorod aspect ratio
