Structural transitions and global minima of sodium chloride clusters

In recent experiments on sodium chloride clusters, structural transitions between nanocrystals with different cuboidal shapes were detected. Here we determine reaction pathways between the low-energy isomers of one of these clusters, ${\mathrm{}\left(\mathrm{NaCl}\right)\mathrm{}}_{35}{\mathrm{Cl}}^{\mathrm{-}}.$ The key process in these structural transitions is a highly cooperative rearrangement in which two parts of the nanocrystal slip past one another on a {110} plane in a $〈11¯0〉$ direction. In this way the nanocrystals can plastically deform, in contrast to the brittle behavior of bulk sodium chloride crystals at the same temperatures; the nanocrystals have mechanical properties which are a unique feature of their finite size. We also report and compare the global potential-energy minima for $(\mathrm{NaCl}{)}_N{\mathrm{Cl}}^{\mathrm{-}}$ using two empirical potentials, and comment on the effect of polarization.