Materials Research by Means of Multiscale Computer Simulation
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Materials Research by Means of Multiscale Computer Simulation
Tomás Díaz de la Rubia and Vasily V. Bulatov, Guest Editors Predicting the properties and performance of materials is central to the success of major industries producing a vast range of consumer goods and to research programs at laboratories and universities around the world. For many years, scientists have longed to have computer simulations that predict the behavior of materials and track the evolution of their microstructures from the atomic to the engineering scales. Until recently, such simulations had been little more than an elusive goal. In recent years, the advent of ever more powerful, massively parallel computers, coupled with spectacular advances in the theoretical framework that describes materials, has enabled the development of new concepts and algorithms for the computational modeling of materials. As the field of computational materials science develops and matures, the notion is taking hold in the community that modeling efforts should be an integral part of interdisciplinary materials research and must include experimental validation. In multiscale modeling, the goal is to predict the performance and behavior of complex materials across all relevant length and time scales, starting from fundamental physical principles and experimental data. The challenge is tremendous. At the atomic (nanometer) scale, electrons govern the interactions among atoms in a solid, and therefore quantum mechanical descriptions are required to characterize the collective behavior of atoms in a material.
MRS BULLETIN/MARCH 2001
However, at the engineering scale, forces arising from macroscopic stresses and/or temperature gradients may be the controlling elements of materials performance. At scales in between, defects such as dislocations control mechanical behavior on the microscale (tens of micrometers), while large collections of such defects, including grain boundaries and other microstructural elements, govern mesoscopic properties (hundreds of micrometers). The net outcome of these interactions can be described as a constitutive law that ultimately governs continuum behavior on the macroscale (centimeters). Conceptually, two different types of multiscale simulations have been considered. One of them attempts to piece together a hierarchy of computational approaches in which larger-scale models use coarsegrained representations of the material and its microstructure while using the data obtained in more detailed, smaller-scale models as a material-defining input. Such parameter-passing, sequential modeling approaches have proven effective, especially when material behavior can be parsed into several scales, each with its own distinct characteristics. Another type of multiscale simulation attempts to link several computational approaches together in a combined model in which different scales of material behavior are considered concurrently and communicate using some sort of “handshaking” procedure. Specific choice and implementation of either se-
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