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Volume 136, Issue 10, 14 March 2012
The lowest-energy isomers of CuNclusters for N = 20–30 are identified using an unbiased search algorithm and density functional theory calculations. The low-energy structures over this size range are dominated by those based on a 13-atom icosahedral (Ih) core and a 19-atom double icosahedron (DIh) core. A transition in the ground-state isomers from Ih-based to DIh-based structures is predicted overt N = 21–23. We discuss this transition in the broader context of the growth pattern for CuN over N = 2–30 that features regions of gradual evolution in which atoms successively add to the clustersurface, separated by sudden changes to a different structural organization and more compact shape. These transitions result from a competition between interatomic bonding energy and surface energy. The implications of this growth pattern for the further evolution of copper from microstructure to bulk are discussed.
136(2012); http://dx.doi.org/10.1063/1.3692601View Description Hide Description
We apply the methodology of self-consistent Brownian dynamics simulations to study the self-assembly behavior in melts of semiflexible-flexible diblock copolymers as a function of the persistence length of the semiflexible block. Our results reveal a novel progression of morphologies in transitioning from the case of flexible-coil to rod-coil copolymers. At even moderate persistence lengths, the morphologies in the semiflexible-block rich region of the phase diagram transform to liquid crystalline phases. In contrast, the phases in the flexible-block rich region of the phase diagram persist up to much larger persistence lengths. Our analysis suggests that the development of orientational order in the semiflexible block to be a critical factor influencing the morphologies of self-assembly.