WFU Physics Colloquium

TITLE: “The fascinating world of Metal Organic Framework materials”
SPEAKER: Yves Chabal
Department of Materials Science and Engineering,
University of Texas at Dallas,
Dallas, TX

TIME: Wed. Nov. 1, 2017 at 4:00 PM
PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Metal Organic Frameworks (MOFs) are a new class of hybrid nanoporous materials that are attracting much interest due to their potential applications for gas storage and separation, pollutant sequestration including radioactive materials, sensing, biomedical devices, fuel production and more recently catalysis. They are crystalline, with metal centers at the corners of the unit cell connected by organic linkers, and are obtained by relatively straightforward synthesis methods (e.g. one-pot process). Consequently, a
large number of structures can be prepared, over 50,000 so far. With their well-defined crystalline structure (determined by X-ray diffraction), these materials are ideal to study fundamental processes, such as the interaction of small gases in nanopores, chemical functionalization of nanoporous networks
and potential catalytic activity. Recently, there has even been some effort to synthesize small metallic nanoparticles inside the pores of the network.

This talk will illustrate some of the fascinating behaviors and properties of MOFs by focusing on trapping small molecules into one of the best-characterized MOF structures (MOF-74), and on synthesizing directly 1nm-diameter Au nanoparticles inside the pores of a novel MOF structure (MOF-808). Along the way, it will also show how precise information can be derived from a host of spectroscopic (infrared, Raman, X-ray photoelectron spectroscopy, UV-vis, low-energy ion scattering) and imaging (TEM) measurements, in addition to the more conventional measurements (e.g. isotherms). The importance of
first-principles calculations will be highlighted as a means to extract quantitative information from IR spectroscopy and to gain fundamental understanding of important processes.

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WFU Physics Colloquium

TITLE: “Ions, Statistics, and simulations of macromolecules”
SPEAKER: Freddie Salsbury Jr.
Department of Physics,
Wake Forest University,
Winston-Salem, NC

TIME: Wed. Oct. 25, 2017 at 4:00 PM
PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Dr. Salsbury will present selected new strands of research in his group, which were enabled by his recent research sabbatical. These strands involve examining the effects of ion binding on the structure and dynamics of a therapeutic nucleic acid, and on the functions of different proteins such as thrombin and NEMO. These studies have also included applying and developing new clustering methods from statistics. If time permits, some simple applications of machine learning to these systems and more will be presented.

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WFU Physics and Chemistry Colloquium

TITLE: “Solid Electrolytes and Their Interfaces: Bridging Mechanistic Understanding to Their Performance”
SPEAKER: Zachary D. Hood
School of Chemistry and Biochemistry,
Georgia Institute of Technology, Atlanta, GA
Center for Nanophase Materials Sciences,
Oak Ridge National Laboratory, Oak Ridge, TN

TIME: Wed. Oct. 18, 2017 at 4:00 PM
PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Solid electrolytes (SEs) have attracted ever-growing research interest for their potential to offer the safety and energy density necessary for future battery systems. Ideal SEs are defined by high ionic conductivity and low electrical conductivity. Not only being the primary component in all-solid-state batteries, SE materials also play an important role as a protector for Li-metal anodes in novel battery configurations, such as Li-S, Li-air, and redox flow batteries. The impedance at interfaces associated with SEs (i.e. the internal grain and phase boundaries) and their interfacial stability with electrodes are currently two key factors limiting the performance of batteries involving SEs. To pave the way for next-generation high-performance batteries, we need to develop a mechanistic understand of the origins of interfacial resistance and potential instability at interfaces. In this Colloquium, I will start with a brief introduction to the fundamentals of SEs and challenges associated with their interfaces. Next, representative examples from my current work with sulfide-based and oxide-based SEs will be discussed in detail, highlighting some of the recent fundamental insights gained based on advanced characterization techniques and high-throughput theoretical methods. Applicable strategies for improving ion conduction and stability in SEs and interfaces will also be discussed. This Colloquium will conclude by highlighting opportunities and perspectives for future research that will enhance our fundamental understanding of SEs and their performance in electrochemical energy storage systems.

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WFU Physics and Chemistry Colloquium

TITLE: “Solution Processing of High-Performance Solar Cells: Opportunities & Technological Challenges”
SPEAKER: Professor David Mitzi
Mechanical Engineering and Materials Science
Duke University
Durham, NC
TIME: Wed. Oct. 4, 2017 at 4:00 PM
PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

While ever expanding worldwide energy demand necessitates a broad portfolio of energy options, the progressive drop in cost and ubiquitous carbon-free “fuel” for photovoltaic (PV) technologies suggests that this pathway will play a vital role in this mix. Device fabrication involving simple solution-based processing provides one pathway for substantially further reducing cost for PV application. This talk addresses several particularly promising thin-film PV technologies based on solution-processed Cu-In-Ga-S-Se (CIGS) and Cu-Zn-Sn-S-Se (CZTS) chalcogenide absorbers, enabling the fabrication of high-performance absorber layers, with resulting device sunlight-to-electricity power conversion efficiencies of as high as 15%. Key focal points include developing appropriate solution/precursor chemistries, and film deposition and defect engineering approaches. For the relatively new CZTS system, the combination of progressively higher record efficiency, earth abundant starting materials, and lower-cost solution-based processing opens opportunities for development of a potentially pervasive PV technology. In addition, metal-halide perovskite compounds, offering near-ambient temperature solution processing, a high degree of chemical tunability and unprecedented improvement in efficiency to the 20+% level over only a few short years of development, will also be discussed. The three technologies (CIGS, CZTS and perovskites) provide outstanding examples of how solution-based processing may, not only lead to a pathway for low cost PV, but also to performance levels that rival and even beat vacuum-based deposition, which is crucial for these technologies to have market penetration.

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WFU Physics Colloquium

TITLE: “Photons, electrons, and phonons; OLED, OFET, and OPV”

SPEAKER: Professor Laurie E. McNeil
Department of Physics and Astronomy
University of North Carolina at Chapel Hill
Chapel Hill, NC

TIME: Wed. Sep. 27, 2017 at 4:00 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

First discovered at the beginning of the 20th century but still only partially understood today, organic semiconductors combine the electrical and optical properties typical of inorganic semiconductors with properties such as flexibility, low cost, and structural tunability via chemical modification. They are of significant interest due to their potential for opto-electronic applications such as displays, photosensors and solar cells. Charge transfer compounds, which are made of two or more organic molecules in which one species acts as a donor of electric charge and the other as an acceptor, could provide new properties or improved performance to increase the range of application of organic semiconductors. I will discuss how optical measurements such as resonant Raman scattering and transient absorption, when combined with numerical calculations, can elucidate the physics of the subtle interplay of interactions that is critical to applications of these materials in 21st-century opto-electronic devices.

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WFU Physics Colloquium

TITLE: Guided Design of Materials: from the sublime (core-shell nanoparticles) to the ridiculous (High-Entropy Alloys*

SPEAKER: Professor Duane D. Johnson
F. Wendell Miller Professor,
Materials Science & Engineering, Iowa State University
Chief Scientist, Ames Laboratory/U.S. DOE,
Ames, Iowa

TIME: Wed. Sep. 20, 2017 at 4:00 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Since the Iron Age, complex alloying effects have yielded desirable and unusual behaviors whose origins were difficult to unravel. Here we address intriguing behavior from alloying that occur in metallic nanoparticles to bulk complex solid solutions.

Core-shell preferences in catalytic metallic nanoparticles have failed to be predicted/explained from almost two decade of experiments, theory, and data science. Yet, simple concepts reveal the key correlations that determine the preferences, and, as a result, such behavior is easily predicted with no calculations, as will be revealed. With today’s data-oriented focus, this shows the necessity for data mining rather than data searching.

High-Entropy Alloys –near equiatomic solid solutions with 5+ elements– have emerged as novel, complex alloys with a variety of attractive properties: simple structures, better mechanical response at higher temperatures, and good oxidation resistance. Alloys at the edge of entropic stability offer prospects to coax them along different transformation pathways. From a design perspective, little is exceptional about HEAs, save maximal entropy, offering a huge space to tune for optimal properties, with only slightly reduced entropy. “High-throughput” KKR-CPA multiple-scattering theory, a Green’s function electronic-structure method, is applied to predict electronic, structural, and enthalpy (global stability) information for N-component HEA, where the coherent potential approximation (CPA) handles chemical disorder during charge self-consistency. Additionally, KKR-CPA-based thermodynamic linear-response yields short-range order (local stability) to guide alloy design, dictated by N(N–1)/2 chemical pair correlations. We exemplify predictions to narrow the N-dimensional design space, and show some experimental validations.

*Supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division for theory development, and by the Office of Fossil Energy, Cross-cutting Research program for code validation for HEAs and experimental validation. Ames Laboratory is operated for DOE by ISU under Contract DE-AC02- 07CH11358.

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The first SPS (Society of Physics Students) meeting of the semester will be held on Thursday, Aug. 31, 2017 in the Olin Lobby at 12 noon. Free pizza and soft drinks will be provided. Contact Professor Carlson for further information.

WFU Physics Colloquium

TITLE: “Machine Learning in Experimental Nuclear Physics”

SPEAKER: Professor Michelle Kuchera
Department of Physics
Davidson College
Davidson, NC

TIME: Wed. Sep. 13, 2017 at 4:00 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

The atomic nucleus was discovered by Ernest Rutherford in 1911. Over 100 years later, as the limits of nuclear existence are beginning to be explored, we are still working toward a complete understanding of the structure and properties of all nuclei. Advanced accelerators and detectors are used to study reactions involving rare nuclei. This talk will discuss the computational challenges and methods of “big data” detector systems.

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WFU Physics Colloquium

TITLE: “Welcome to the WFU Physics Department”

TIME: Wed. Aug. 30, 2017 at 3:30 PM^*      

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

^* Note: early starting time.

Refreshments will be served at 3:00 PM in the lounge. All interested persons are cordially invited to attend.

PROGRAM

The purpose of this first seminar is to help new, returning, and prospective students (including both undergraduate and graduate students), faculty, and staff to become acquainted with each other and with the Physics Department. After refreshments in the lounge in the lobby of Olin Physical Laboratory (starting at 3:00), we will meet in the George P. Williams, Jr. Lecture Hall (Olin 101) at 3:30 PM for some announcements followed by presentations by some undergraduate students, highlighting their summer research experiences.

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