  We study the role of the effective mass, band mixing and phonon emission on
multiexciton generation in IV-VI nanocrystals. A 4-band k dot p effective mass
model, which allows for an independent variation of these parameters, is
adopted to describe the electronic structure of the nanocrystals. Multiexciton
generation efficiencies are calculated using a Green's function formalism,
providing results that are numerically similar to impact excitation. We find
that multiexciton generation efficiencies are maximized when the effective mass
of the electron and hole are small and similar. Contact with recent
experimental results for multiexciton generation in PbS and PbSe is made.
