Shuji Ogata

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A suite of scalable atomistic simulation programs has been developed for materials research based on space-time multiresolution algorithms. Design and analysis of parallel algorithms are presented for molecular dynamics (MD) simulations and quantum-mechanical (QM) calculations based on the density functional theory. Performance tests have been carried out(More)
A multidisciplinary, collaborative simulation has been performed on a Grid of geographically distributed PC clusters. The multiscale simulation approach seamlessly combines i) atomistic simulation based on the molecular dynamics (MD) method and ii) quantum mechanical (QM) calculation based on the density functional theory (DFT), so that accurate but less(More)
Multimillion atom molecular-dynamics (MD) simulations are performed to investigate dynamic fracture in glasses and nanostructured ceramics. Using multiresolution algorithms, simulations are carried out for up to 70 ps on massively parallel computers. MD results in amorphous silica (a-SiO 2) reveal the formation of nanoscale cavities ahead of the crack tip.(More)
Materials and devices with microstructures on the nanometer scale are revolutionizing technology, but until recently simulation at this scale has been problematic. Developments in parallel computing are now allowing atomistic simulation using multiresolution algorithms, such as fast multipole methods. With these algorithms, researchers may soon be able to(More)
We propose a reservation-based sustainable adaptive Grid supercomputing paradigm to enable tightly coupled computations of considerable scale (involving over 1,000 processors) and duration (over tens of continuous days) on a Grid of geographically distributed parallel supercomputers. The paradigm is demonstrated for an adaptive multiscale simulation(More)
A scalable and portable Fortran code is developed to calculate Coulomb interaction potentials of charged particles on parallel computers, based on the fast multipole method. The code has a unique feature to calculate microscopic stress tensors due to the Coulomb interactions, which is useful in constant-pressure simulations and local stress analyses. The(More)
A hybrid simulation approach is developed to study chemical reactions coupled with long-range mechanical phenomena in materials. The finite-element method for continuum mechanics is coupled with the molecular dynamics method for an atomic system that embeds a cluster of atoms described quantum-mechanically with the electronic density-functional method based(More)
Oxidation of aluminum nanoclusters is investigated with a parallel molecular-dynamics approach based on dynamic charge transfer among atoms. Structural and dynamic correlations reveal that significant charge transfer gives rise to large negative pressure in the oxide which dominates the positive pressure due to steric forces. As a result, aluminum moves(More)
A hybrid quantum-mechanical/molecular-dynamics simulation is performed to study the effects of environmental molecules on fracture initiation in silicon. A ͑110͒ crack under tension ͑mode-I opening͒ is simulated with multiple H 2 O molecules around the crack front. Electronic structure near the crack front is calculated with density functional theory. To(More)