  We report a numerical study of the effect of interface alloying and
band-alignment on the Auger recombination processes of core/shell nanocrystals.
Numerical calculations are carried out using a two-band Kane Hamiltonian.
Smooth interfaces are found to suppress Auger recombination, the strength of
the suppression being very sensitive to the core size. The use of type-II
structures constitutes an additional source of suppression, especially when the
shell confines electrons rather than holes. We show that "magic" sizes leading
to negligible Auger recombination [Cragg and Efros, Nano Letters 10 (2010) 313]
should be easier to realize experimentally in nanocrystals with extended
interface alloying and wide band gap.
