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For infrequent-event systems, transition state theory ͑TST͒ is a powerful approach for overcoming the time scale limitations of the molecular dynamics ͑MD͒ simulation method, provided one knows the locations of the potential-energy basins ͑states͒ and the TST dividing surfaces ͑or the saddle points͒ between them. Often, however, the states to which the(More)
For two methods commonly used to achieve canonical-ensemble sampling in a molecular-dynamics simulation, the Langevin thermostat and the Andersen [H. C. Andersen, J. Chem. Phys. 72, 2384 (1980)] thermostat, we observe, as have others, synchronization of initially independent trajectories in the same potential basin when the same random number sequence is(More)
Although grain boundaries can serve as effective sinks for radiation-induced defects such as interstitials and vacancies, the atomistic mechanisms leading to this enhanced tolerance are still not well understood. With the use of three atomistic simulation methods, we investigated defect-grain boundary interaction mechanisms in copper from picosecond to(More)
Many important materials processes take place on time scales that vastly exceed the roughly one microsecond accessible to molecular dynamics simulation. This time scale problem is quite general, showing up in many areas of chemistry, physics, biology, etc. Over the past 15 years, we have developed an accelerated molecular dynamics (AMD) approach, in which(More)
Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. However, the precise role of the interfaces in modifying defect behavior is unclear. Using long-time simulations methods, we determine the(More)
Parallel replica dynamics simulation methods appropriate for the simulation of chemical reactions in molecular systems with many conformational degrees of freedom have been developed and applied to study the microsecond-scale pyrolysis of n-hexadecane in the temperature range of 2100-2500 K. The algorithm uses a transition detection scheme that is based on(More)
We study radiation-damage events in MgO on experimental time scales by augmenting molecular dynamics cascade simulations with temperature accelerated dynamics, molecular statics, and density functional theory. At 400 eV, vacancies and mono- and di-interstitials form, but often annihilate within milliseconds. At 2 and 5 keV, larger clusters can form and(More)
A series of massively parallel molecular dynamics simulations with up to 35 million atoms is performed to investigate dislocation emission from a three-dimensional crack. We observe dislocation loops emitted from the crack front|the rst time this has been seen in computer simulations. The sequence of dislocation emission in the process of crack blunting(More)
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