The paper, titled "Interface Mobility from Interface Random Walk", addresses computational issues in extracting interface kinetic parameters under experimentally relevant conditions. It is currently available online at: http://www.sciencemag.org/cgi/content/abstract/314/5799/632.
Interfaces are an important class of defects whose distribution affects the properties of the otherwise pristine material, both in nature and in technology. This is especially the case in polycrystals, thin films, multiphase materials, and composites, where the mechanical, chemical, and transport properties are sensitive to the underlying interfacial microstructure.
"In fact, tailoring this microstructure is an emerging paradigm for engineering high performance, multifunctional materials," said Zachary Trautt, a graduate student at Colorado School of Mines and the first author in the study.
The interfacial microstructure is subject to several driving forces during material synthesis and function. More often than not, these driving forces are large enough to cause the interfaces to move and the microstructure (or its precursor) evolves. Naturally, controlling the final microstructure requires accurate models that relate the interface motion to the driving forces in effect.
A quantitative measure of interface kinetics is the interface mobility, the ratio of the interface velocity to the driving force. Past studies on individual homophase crystalline interfaces (or grain boundaries) in several high-purity metals show an interesting trend; the experimental mobilities are orders of magnitude smaller than those extracted via computations. The discrepancy is often attributed to the presence of impurities, fueling speculation that even minute quantities of impurities significantly retard interface motion.
"An often overlooked fact is that computations are limited to tens of nanoseconds," saidMoneesh Upmanyu, co-author and the lead researcher in the study. "As a result, they are performed at driving forces orders of magnitude greater than those commonly observed in experiments," he explained. "This further weakens the comparison, and there is a need to extend the computational studies to more realistic driving forces, and include the effect of impurities."
"Our computational methodology offers a way to address both these challenges, efficiently and with setups that are relatively simple," said Trautt.
The basis for the methodology is the pioneering theoretical work by Einstein, Smulochowski and Langevin on Brownian motion in the early 1900s.
"Just as their study related the dance of macroscopic particles to their diffusivity, the microscopic thermal fluctuations result in interface forces that conspire towards a one-dimensional dance of the average interface position, which in turn yields its mobility in the zero driving force limit," said Alain Karma, also a co-author in the study.
"The technique is remarkably efficient," noted Upmanyu. "The computations on pure aluminum yielded mobilities within a nanosecond, a significant savings in computational resources."
Comparisons with previous experiments and computations reveal that the retarding effect of impurities is much more severe than previously thought. The authors are now working on extending the theory and the computations to directly quantify the impurity drag effect.
Laura Shea | EurekAlert!
Powerful IT security for the car of the future – research alliance develops new approaches
25.05.2018 | Universität Ulm
Supercomputing the emergence of material behavior
18.05.2018 | University of Texas at Austin, Texas Advanced Computing Center
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences