Forum Schedule Fall 2017

Fridays 3:45pm - 4:45pm BPB-217

Date Speaker Topic (click down-arrow to see abstract)
Sep 1 Physics&Astronomy Department Meeting

Sep 8

Sep 15 John Tse
University of Saskatchewan
host:. Qiang Zhu
Structure, Structural Evolution and Superconductivity of High Pressure Hydrogen-rich Alloys

Pressure has an enormous effect in altering the structure, physical and chemical properties of matters. In general, for elemental metals, compression led to loosely bound valence electrons redistributed into the interstitial vacancies and often resulted in novel open 2-D and 3D structures. Incidentally, when mixed with H2, which has an electronegativity similar to group 13 and 14 elements, charge transfer Zintl-Klemen type compounds can be formed. This phenomenon helps to explain the structural trend in hydrogen-rich alloys predicted by First Principle methods. Under suitable conditions, these alloys may even become superconductors and, in some cases, with very high critical temperature (Tc). Analysis of the functional derivative of Eliashberg spectral functions show that efficient electron-phonon coupling over the entire vibrational spectrum can be achieved on crystal structures when the stretch and bend vibrations of weakly linked hydrogen network atoms are strongly mixed.

Sep 22 Hanno Rein
University of Toronto
host: Jason Steffen
Formation and Stability of Planetary Systems

The diverse population of extrasolar planets keeps challenging theories of planet formation. Multi-planetary systems are of particular interest as their dynamical architectures allow us to constrain an otherwise unobservable formation phase.

I'll show how a simple stability requirement together with machine learning tools can be used to constrain orbital parameters of planetary systems such as HL-Tau and Trappist-1. Some of the dynamical properties we find in the these systems can be explained by a turbulent protoplanetary disk and stochastic planet migration. Saturn's rings can be thought of as a small scale version and test bed of the early Solar System. I'll show evidence that stochastic migration can be directly observed in moonlets around Saturn.

I'll finally talk about some of the numerical challenges when running accurate long term simulations of planetary systems. Even though we are solving differential equations that have been known since Newton's time, several breakthroughs were made only very recently with the help of clever numerical algorithms. Among these is the discovery that one percent of all realization of the Solar System lead to collisions between planets within the life-time of the Sun.

Sep 29

Oct 6 Simon Kimber
Oak Ridge National Lab
host:. Ashkan Salamat
High Energy Insights Into Materials Science

3rd generation synchrotrons and spallation neutron sources provide high-energy beams of x- rays and neutrons. In the last ten years, these sources have been increasingly applied to materials science problems. This is due to the highly penetrating power of the radiation, unique atomic contrast, and access to reciprocal space far beyond that available with laboratory sources. In this presentation I shall describe recent advances in sample environment and technique, which have given users access to mechanochemical synthesis [1]. This has provided unique insights into ZIF production [2], short-lived co-crystal intermediates [3] and even non- equilibrium phase formation [4]. I will next show how advances in data processing have allowed the development of pair distribution function (PDF) contrast computed tomography [5]. This developing technique allows the mapping and characterisation of nano-particle dispersion in supported catalysis bodies [6]. Finally, I will discuss PDF scattering in the liquid state [7], and prospects for ‘crystallography beyond the crystal’, in systems from polyoxometalates to pharmaceuticals. The presentation will conclude with an update on new techniques under development at ORNL, including dynamic PDF measurements and advanced high pressure sample environment. Finally, an update on the newly commissioned POWGEN neutron powder diffractometer will be given. This is currently the highest resolution such machine in North America.

Oct 13 Shyue Ping Ong
UC San Diego
host: Qiang Zhu
Deep Learning Quantum Mechanical Calculations to Design Materials

Powered by methodological breakthroughs and computing advances, electronic structure methods have today become an indispensable toolkit in the materials designer’s arsenal. In this talk, I will discuss two emerging trends that holds the promise to continue to push the envelope in computational design of materials. The first trend is the development of robust software and data frameworks for the automatic generation, storage and analysis of materials data sets. The second is the advent of reliable central materials data repositories, such as the Materials Project, which provides the research community with efficient access to large quantities of property information that can be mined for trends or new materials. I will show how we have leveraged on these new tools to accelerate discovery and design in energy and structural materials as well as our efforts in contributing back to the community through further tool or data development.

Oct 20 Canceled

Oct 27 Nevada Day Recess

Nov 3 David Nesvorny
Southwest Research Institute
host: Jason Steffen

Nov 10 Veterans Day Recess

Nov 17 TBA
hosts: Qaing Zhu & Ashkan Salamat

Nov 24 Thanksgiving Day Recess

Dec 1 Fred Adams
University of Michigan
host: Zhaohuan Zhu

Dec 8 Ho-kwang Mao
Geophysical Lab
host: Qiang Zhu

Dec 15 Final Examinations

Past forums: Spring 2017  Fall 2016  Spring 2016  Fall 2015   Spring 2015   Fall '14   Spring '14   Fall '13   Spring '13   Fall '12 Spring '12   Fall '11   Spring '11   Fall '10   Spring '10   Fall '09   Spring '09   Fall '08