Walter Wolf and Volker Eyert will give invited talks at the Bunsen Colloquium 'Defects and Diffusion in Solids: Application of New Theoretical Concepts' held at the RWTH Aachen November 10-11, 2016 and organized by Manfred Martin and Roger A. De Souza to honour Peter C. Schmidt on the occasion of his 75th birthday. (Here is a link to the Colloquium: http://www.bunsen.rwth-aachen.de). Walter's talk is entitled 'Defect Formation, Diffusion, Coalescence, Precipitation - ab initio driven Materials Simulations for Industrial Needs' and Volker is giving a talk on 'Defects in Solids: Blessing and Curse - A View from Industrial Applications'. We will be delighted to see you in Aachen!
Here are their abstracts:
Defect formation, diffusion, coalescence, precipitation – ab initio driven materials simulations for industrial needs
Materials Design s.a.r.l., 42, avenue Verdier, 92120 Montrouge, France
Point defects and their mobility play a decisive role for the macroscopic performance of modern materials. Scope and magnitude thereby range from as-designed defect and dopant implantation for tuning electronic devices, to detrimental effects on the mechanical properties of high-strengths alloys due to hydrogen embrittlement and stress-corrosion cracking, up to defect cascades and hydrogen uptake emerging during irradiation of cladding materials under nuclear reactor conditions, resulting in hydrogen induced swelling and breakaway growth.Designing properties as well as addressing materials problems require control and understanding of defect formation, diffusivity and diffusion anisotropy, interaction between defects and the propensity to coalesce thus forming extended defects such as dislocation loops, absorption and dissolution up to the solubility limit, eventually leading to precipitation processes when exceeding the solubility product. Atomistic simulations, and in particular the predictive power of ab initio methods, can have a tremendous impact for the research process, given that each phase of the defect evolution, as paradigmatically sketched above, could be addressed on their appropriate length and time scales. From a methodological point of view multiscale approaches are needed, allowing to extend the predictive power of ab initio methods to much larger time and length scales and millions of configurations. Within the MedeA modeling environment of Materials Design, Inc. a seamless integration of such approaches - for instance the Cluster Expansion Technique and Forcefield optimization - offers a high level of automation and interoperability for enhancing the productivity of the overall research process. Computational methods will be briefly outlined and recent applications for research activities addressing industrial materials problems and design will be summarized. Thus, highlights of an extensive study of hydrogen induced irradiation growth of Zircaloy including the impact of alloying elements will be presented, revealing for instance a pronounced retardation effect of self-interstitial Zr diffusion by Nb and Sn alloying additions. In the context of a screening study on candidate phases for precipitation hardening of steels, the accurate computation of solubility products establishing alloy compositions for casting and heat treatment will be outlined, and the monitoring of phase stability and composition-temperature dependent precipitation processes by means of large scale Monte Carlo simulations will be demonstrated for Ni-Cr alloy systems.
Defects in solids: Blessing and curse – a view from industrial applications
Materials Design SARL, 42 Avenue Verdier, 92120 Montrouge, France
While the concepts of crystalline periodicity, reciprocal space, and electronic band structures have proven very powerful for the understanding of solids and for this reason shaped the mindset of generations of chemists, physicists, and materials scientists, imperfections have long been regarded throughout as unwanted but unavoidable perturbations, causing, e.g., materials fatigue due to embrittlement and cracking at the microscopic scale or failure of electronic devices. Only more recently, as with the rapid progress in experimental and theoretical techniques our ability to understand and tune materials properties at the nanoscale has tremendously grown, a more active handling of crystalline imperfections has come into reach, which opened a new research field for materials research. Providing deep insight paired with a high predictive power, atomistic simulations have a large share in this development. Indeed, it would not have become possible without the tremendous increase of capabilities in atomistic simulations, both with respect to methodological developments in multiscale modeling and the explosive increase of computational resources. The MedeA computational environment of Materials Design, Inc. has condensed this progress and offers the unique possibility of a comprehensive tool to understand and predict a large variety of properties of all kinds of materials. In my talk I will present some of the capabilities of MedeA and illustrate them with a range of examples. In doing so, I will focus on success stories, where defects and dopants have been used to optimize materials properties or else where the detrimental effect of impurities has been traced back to their roots and overcome as, e.g., at grain boundaries. Examples are taken from battery research and electronics applications.