Event | Date | Summary |
Christopher Wolverton, Northwestern University, Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools | Mon. December 5th, 2016 12:45 pm-1:45 pm |
Accelerating Materials Discovery with Data-Driven Atomistic Computational Tools Chris Wolverton Dept. of Materials Science and Eng., Northwestern University, Evanston, IL (USA) c-wolverton@northwestern.edu
Many of the key technological problems associated with alternative energies (e.g., thermoelectrics, advanced batteries, hydrogen storage, etc.) may be traced back to the lack of suitable materials. Both the materials discovery and materials development processes may be greatly aided by the use of computational methods, particular those atomistic methods based on density functional theory (DFT). Here, we present an overview of our recent work utilizing high-throughput computation and data mining approaches to accelerate materials discovery, |
Marie-Charlotte Renoult, Université de Rouen, Free falling jets of a viscoelastic solution | Wed. November 23rd, 2016 12:45 pm-1:45 pm |
Title: Free falling jets of a viscoelastic solution Abstract: We conducted free falling jet experiments of a Newtonian solution with a polymer additive, i.e., a viscoelastic solution.Viscoelastic jets usually break up with the formation of beads-on-a-string (BOAS) structures, where large beads are connected by thin threads. These structures form when the polymer solution begins to exhibit strain-hardening, i.e., an increase in extensional viscosity with extensional rate. Associated with this viscoelastic property is a characteristic relaxation time.In this presentation, two methods of image analysis will be presented: a shape analysis and a multi-scale analysis that are applied to a large number of free falling jet visualisations performed at different jet velocities.The results obtained demonstrate the power of these two experimental techniques to gain a deeper insight into BOAS formation and to probe complex liquid rheology such as the subtle measurement of the polymer relaxation time. |
Keji Lai, Univ of Texas, Austin/Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials | Mon. November 21st, 2016 12:45 pm-1:45 pm |
The understanding of various types of disorders in 2D materials, including dangling bonds at the edges, defects in the bulk, and charges in the substrate, is of fundamental importance for their applications in electronics and photonics. Because of the imperfections, electrons moving on the 2D plane experience a spatially non-uniform Coulomb environment, whose effect on the charge transport has not been microscopically probed. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we can visualize the spatial evolution of the insulator-to-metal transition in mono-layer and few-layer MoS2 field-effect transistors. As the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk, |
Salah Eddine Boulfelfel, Georgia Institute of Technology, Atomic-Scale Modeling of Activated Processes in the Solid State | Mon. November 14th, 2016 12:45 pm-1:45 pm |
Atomic-Scale Modeling of Activated Processes in The Solid State Salah Eddine Boulfelfel School of Chemical and Biomolecular Engineering Georgia Institute of Technology In the practice of solid-state chemistry, processes either thermally-activated or induced by external high-pressure are common events. Often, the simplicity of the material’s structure involved in the activated process is in contrasts with the theoretical and experimental difficulties in assessing its mechanism. Large hysteresis effects, nucleation and growth scenarios, and first-order kinetics require dedicated computational approaches in order to correctly unravel the complex nature of activated process at the atomistic level of details. |
Jim Andrews, Youngstown State University, Coherent Perfect Polarization Rotation–Beyond the Anti-Laser | Mon. November 7th, 2016 12:45 pm-1:45 pm |
We describe the distinguishing characteristics of coherent perfect optical conversion processes using two-beam interference, as compared to single-beam ‘critical coupling’ processes. We extend the application of two-port coherent conversion processes to magneto-optical (Faraday) rotation in structured systems and present our recent laboratory demonstration of coherent perfect polarization rotation (CPR) which is a conservative, reversible counterpart to coherent perfect absorption (CPA, or the so-called ‘antilaser’). conclude with a brief summary of theoretical studies suggesting a CPR-based miniaturization of optical isolators and the extension of coherent perfect phenomena in non-linear optics. |
Samo Kralj, University of Maribor, Effective Topological Charge Cancellation Mechanism | Mon. October 31st, 2016 1:00 pm-2:00 pm |
Effective Topological Charge Cancellation Mechanism Samo Kralj1,2 1FNM, University of Maribor, Koroška 160, 2000 Maribor, Slovenia 2Jožef Stefan Institute, Jamova 39,1000 Ljubljana, Slovenia Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions [1]. Topological origin makes their key features independent of systems’ microscopic details and therefore TDs display many universalities. In general, TDs have strong impact on material properties and play significant role in several technological applications. Furthermore, investigations of TDs in relevant fields are interesting for fundamental science. |
Patrick Woodward, The Ohio State University, The magnetism of double perovskites containing osmium and rhenium | Mon. October 24th, 2016 12:45 pm-1:45 pm |
Patrick M. Woodward Department of Chemistry and Biochemistry, The Ohio State University Over the past several years we have been synthesizing and studying the magnetic properties of A2MOsO6 and A2MReO6 (Mg, Zn, Cr, Fe, Co, Ni) double perovskites in a quest to understand how the sign and strength of the superexchange interactions change as a function of the relative filling of the 3d and 5d orbitals, as well as the geometry of the crystal structure. In double perovskites where the 5d ion is the only magnetic ion we find that spin-orbit coupling plays a role, |
Nayana Shah, University of Cincinnati, Manifestations of spin-orbit coupling and topology in out-of-equilibrium hybrid superconducting systems | Mon. October 10th, 2016 12:45 pm-1:45 pm |
Recently there has been a lot of excitement generated by the possibility of realizing and detecting Majorana fermions within the arena of condensed matter physics and its potential implication for topological quantum computing. Although already at the end of twentieth century emergent Majorana end-states were shown to exist in a theoretical model of spinless p-wave superconductor (Kitaev) chain, it was only a decade later that proposals to experimentally realize such a model emerged. These were motivated by the discovery of topological insulators that ushered a new era of so-called symmetry-protected topological phases but also stemmed from existent studies of hybrid superconductor-ferromagnet systems that form the basis of another highly active area of superconducting spintronics. |
Zhaoning Song, University of Toledo,The Formation and Degradation of Metal Halide Perovskites | Mon. September 26th, 2016 12:45 pm-1:45 pm |
Solar cells based on organic-inorganic metal halide perovskite materials, such as methylammonium lead iodide (CH3NH3PbI3), have been the subject of intense investigation during the past 5 years due to high power conversion efficiencies (>22%) and relatively low manufacturing costs. Never before has the field of photovoltaics (PV) seen such rapid and exciting progress. The results are surprising because various low-temperature, solution-based processing methods have been successful in fabricating high-efficiency devices. Nevertheless, much of the work in this area has focused on device performance optimization and there is a lack of basic understanding of underlying physics and chemistry. Without this understanding, |