The vibrational density of states of silver in the form of a free cluster, a single crystal and a nanocrystalline material has been calculated with the help of molecular-dynamics simulations. The model for the nanocrystalline material was derived by the simulation of pressureless sintering of nanometer sized silver particles. The results show a broadening of the vibrational density of states in the case of the cluster and the nanocrystalline material.

Mesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock PEO-PLGA-PEO copolymer containing more hydrophobic poly(DL-lactic acid-coglycolic acid) block and the structural difference between mesoporous organosilicas prepared from PEO-PLGA-PEO and PEO-PPO-PEO block templates is discussed.

Computations involving density functional theory have been performed on lead magnesium niobate (PMN) single crystal models in an effort to calculate their surface energies, which are believed to play a role in brittle fracture mechanisms. To establish credibility of this approach, test calculations were performed on MgO and SiC single crystal models. The surface energy of MgO was determined to be 1.2 J/m2, which is in close agreement with the experimental value. Similarly, the value for SiC, 8.03 J/m2, supported a level of confidence with this methodology. Surface energies were calculated for several simple perovskites and several PMN models. The calculated values suggest that changes in the A-site ion of PMN do not result in any significant changes in the surface energies.

Ultra-high strength metallic multilayers are ideal for investigating the effects of length scales in plastic deformation of metallic materials. Experiments on model systems show that the strengths of these materials increase with decreasing bilayer period following the Hall-Petch model. However, as the layer thickness is reduced to the nm-scale, the number of dislocations in the pile-up approaches one and the pile-up based Hall-Petch model ceases to apply. For nm-scale semi-coherent multilayers, we hypothesize that plastic flow occurs by the motion of single dislocation loops, initially in the softer layer, that deposit misfit type dislocation arrays at the interface and transfer load to the harder phase. The stress concentration eventually leads to slip in the harder phase, overcoming the resistance from the misfit arrays at the interface. A model is developed within the framework of classical dislocation theory to estimate the strengthening from this mechanism. The model predictions are compared with experimentally measured strengths.