Gold nanocrystals passivated by self-assembled monolayers of straight-
chain alkylthiolate molecules have been obtained as highly purified mo
lecular materials of high intrinsic stability. Evidence is presented f
or a predicted discrete sequence of energetically optimal fee structur
es of a truncated octahedral morphological motif (see cover). The nano
crystal materials have a propensity to form extended superlattices, su
ch as that in the Figure.