Dr. Barbara Lavina [University of Nevada, Las Vegas, USA]

Title: Extreme conditions microdiffraction, an overview of results and paths forward

Time: 9:00 - 10:00 AM, Tuesday May 22, 2018

Place: Conference room 410, HPSTAR (Shanghai)

Host: Wenge Yang

Polycom: 02120004

Abstract:

Atomic structure determinations are among the most fundamental aspects of materials characterization. Routine measurements become increasing challenging as more extreme conditions are imposed to samples. Recent developments in high-pressure microdifraction techniques opened new frontiers, producing impressive and transformative results. Highresolution data allow unique interpretations and to uncover unexpected behaviors of materials at high pressure for instance increased structural and chemical complexity. Now broadly implemented, extreme conditions micro diffraction experiments remain non-trivial; data collections and reduction strategies ought to be customized for every experiment in order to optimize the use of beam time and achieve target goals. I will present an overview of my experience with high-pressure synchrotron microdiffraction starting with the first full single crystal structural refinements and ending with the characterization of heterogeneous synthesis products. Applications span geoscience, physics and material science. Conditions reach pressures up to 170 GPa and temperatures from ~ 15K, achieved with cryostats, to about 1000 K, generated with double resistive heating. Examples of materials with low-Z and mixed scattering elements will be shown along with examples of phase transitions from single crystal to single crystal and from single crystal to twinned crystals. I will also summarize strategies and results from micro diffraction mapping of heterogeneous samples synthesized in the laser-heated diamond anvil cell. Samples typically show a range of grain sizes, phase concentration and chemical gradients. A comprehensive characterization of such samples allows obtaining solution of complex new phases and, at the same time, learning about compositional and phase gradients. Along with the examples presented I will discuss the scientific directions I plan to pursue as well as possible further technical developments.

Biography of the Speaker:





Dr. Barbara Lavina is an established scientist investigating problems across disciplines, chiefly geoscience, physics, chemistry and material science. She obtained her B.S. and Ph.D. degrees at one of the highest ranked Italian universities, the University of Padova, and has several years of post graduate independent researcher experiences in Italy, at the University of Chicago and at the UNLV. Her research efforts are documented in a robust publications record in peer-review international journals, including highly ranked journals such as the Proceedings of the National Academy of Sciences U.S.A., Science Advances (the latest open-access journal of the AAAS), Geophysical Research Letters and Physical Review B. The results she obtained consistently show exceptional quality of the experimental work. Breakthrough discoveries has been highlighted in professional publications such as Science News, Chemical & Engineering news and the Stewardship Science Academic Programs Annual. Her publications are well cited and recognized. Dr. Lavina regularly presents her contributions at the most reputable International Conferences in the field, including several invited talk presentations. Lavina developed a network of senior collaborators working at very prestigious institutions. She has great experience mentoring graduate and undergraduate students. Lavina is member of the review panels of beamtime users proposals for two of the most prominent Unites States National Laboratories. Barbara Lavina most unique skills are extreme conditions single-crystal and multigrain micro-diffraction. The novel techniques are very powerful and critical to high-pressure science allowing for detailed understanding of crystalline materials response to pressure and for the study of synthesis products, phase equilibria and so on. As a recognition of these efforts, in 2016 Dr. Lavina received the Louis Delbaere Memorial Lecture Award at the Canadian Light Source User Meeting.