Multiresolution molecular-dynamics approach for multimillion atom simulations has been used to investigate structural properties, mechanical failure in ceramic materials, and atomiclevel stresses in nanoscale semiconductor/ceramic mesas (Si/Si3N4). Crack propagation and fracture in silicon nitride, silicon carbide, gallium arsenide, and nanophase ceramics are investigated. We observe a crossover from slow to rapid fracture and a correlation between the speed of crack propagation and morphology of fracture surface. A 100 million atom simulation is carried out to study crack propagation in GaAs. Mechanical failure in the Si/Si3N4 interface is studied by applying tensile strain parallel to the interface. Ten million atom molecular dynamics simulations are performed to determine atomic-level stress distributions in a 54nm nanopixel on a 0.1 µm silicon substrate. Multimillion atom simulations of oxidation of aluminum nanoclusters and nanoindentation in silicon nitride are also discussed.