Simulating Non-equilibrium Processes over Extended Time- and Length-Scales using Parallel Accelerated Dynamics

点击翻译按钮获取中文摘要

NONTECHNICAL SUMMARYThis award supports computational and theoretical research and education that is aimed to develop new ways to use computers to model processes in materials, such as growth, that operate far from the steady balanced state of equilibrium, and to apply these methods to realistic materials problems. Non-equilibrium materials processes play an important role in the production of a variety of technologically important materials and devices, including the growth of semiconductor thin films, solar cells, thin-film based sensors, and materials for protection from radiation. This award provides support for the development of various methods to extend the time- and length-scales over which process like materials growth and defect formation can be simulated on computers, as well as to increase the accuracy of simulations of such non-equilibrium processes. The PI will use these enhanced methods to study technologically relevant processes including the growth of semiconductor thin-films used in solar cells, metal polycrystalline thin-film growth, the nucleation of islands of materials in metal on semiconductor growth, and defect formation and healing of damage in boron nitride nanostructures arising from exposure to electron radiation. The development of improved methods for simulating non-equilibrium processes on computers over extended length- and time-scales is likely to have a significant impact on the realistic simulations of a broad variety of materials-related processes. This project contributes to developing a capability in the quest to design materials from the atoms up to obtain materials with desired properties, and contributes toward the success of the Materials Genome Initiative. Software developed in the course of this project will be made available to the broader community, contributing to the software cyberinfrastructure for the materials simulation community. This project provides opportunities for educational and outreach activities with broad national, international, and societal impact. In addition to the postdoctoral research associate and graduate students involved in this project, several undergraduates will participate through the Department of Physics and Astronomy's Research Experience for Undergraduates program. Undergraduate students will also participate during the academic year. TECHNICAL SUMMARYThis award supports computational and theoretical research to develop methods to extend the speed and accuracy of temperature-accelerated dynamics (TAD) simulations. These include the development of methods to improve the scaling of temperature-accelerated dynamics simulations with system size, a method to carry out on-the-fly kinetic Monte Carlo simulations by the use of local temperature-accelerated basin searches, a method to automatically store local configurations and processes during accelerated dynamics simulations in order to carry out kinetic Monte Carlo simulations with a large database, and the development of methods to efficiently identify, characterize, and exit local superbasins in order to deal with the 'small-barrier' problem. These methods will significantly enhance the speed and accuracy of accelerated dynamics simulations thus allowing realistic simulations of complex ordered and disordered systems over extended time- and length-scales. The developed methods will be used to study a variety of different materials processes which are relevant to semiconductor technology and photovoltaics. In particular, simulations of cadmium telluride thin-film growth will be carried out in order to understand the kinetics of defect formation as well as the dependence on growth conditions. In order to study the early stages of polycrystalline metal on semiconductor growth, simulations of island nucleation and growth in silver on amorphous silicon will also be carried out. The PI will use simulations to investigate glancing angle deposition with an aim to understand the effects of activated processes on surface morphology, grain size, microstructure and scaling behavior as a function of temperature. Finally, in order to explore the potential for boron nitride nanostructured materials to serve as protective shields at high temperatures and in hazardous environments, simulations of the response of boron nitride nanostructures to electron irradiation will also be carried out. The results of these simulations will be used to understand the mechanisms of defect formation and evolution as well as to explain a number of apparent discrepancies between energetics calculations and experiments. Software developed in the course of this project will be made available to the broader community, contributing to the software cyberinfrastructure for the materials simulation community. This project provides opportunities for educational and outreach activities with broad national, international, and societal impact. In addition to the postdoctoral research associate and graduate students involved in this project, several undergraduates will participate through the Department of Physics and Astronomy's Research Experience for Undergraduates program. Undergraduate students will also participate during the academic year.