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Viewing upcoming talks containing the keyword: 19
Speaker: Dr David Payne (Imperial College London)
Understanding the Electronic Structure of Metal Oxides
Abstract Photoelectron spectroscopy (PES) is perhaps the most direct probe of electronic structure available to the experimental scientist, as well as an invaluable tool for elucidating bulk and surface chemical composition. X -ray photoelectron spectroscopy (XPS) i s a very widely utilized PES technique, commonly used in simply determining the stoichiometry of the elements present at a surface or identifying the oxidation state of an element. But these basic observations, do not fully convey the depth of experimental information available to help understand the properties of the material s in question. I will use this talk to demonstrate the power of PES in understanding the fundamental physics and chemistry of materials in this case In 2O3,1,2 PbO 2,3 Bi2O34, IrO 2,5,6 and OsO 2.7 This talk will mainly focus on the work, with many collaborators, have performed on metal oxides, but will branch into more diverse areas of applied functional materials, biomaterials through to biology.
1 The nature of the bandgap in In 2O3 revealed by first -principles calculations and x -ray spectroscopy. A. Walsh, J.L.F. Da Silva, S -H. Wei, C. Korber, A. Klein, L.F.J. Piper, A. DeMasi, K.E. Smith, G. Panaccione, P. Torelli, D.J. Payne, A. Bourlange, R.G. Egdell, Physical Review Letters 100 167402 (2008). 2 Surface electron accumulation and the charge neutrality level in In 2O3. P.D.C. King, T.D. Veal, D.J. Payne, A. Bourlange, R.G. Egdell, C.F. McConville, Physical Re view Letters 101 116808 (2008). 3 Nature of the Band Gap and Origin of the Conductivity of PbO 2 Revealed by Theory and Experiment. D.O. Scanlon, A.B. Kehoe, G.W. Watson, M.O. Jones, W.I.F. David, D.J. Payne, R.G. Egdell, P.P. Edwards, A. Walsh, Physical Re view Letters 107 246402 (2011). 4 Electronic origins of structural distortions in post -transition metal oxides: experimental and theoretical evidence for a revision of the lone pair model. D.J. Payne, R.G. Egdell, A. Walsh, G.W. Watson, J. Guo, P -A. Glans, T. Learmonth, K.E. Smith, Physical Review Letters 96 157403 (2006). 5 Understanding the Electronic Structure of IrO 2 using Hard X -ray Photoelectron Spectroscopy and Density Functional Theory. J.M. Kahk, C.G. Poll, F.E. Oropeza, J.M. Ablett , D. Ceolin, J -P. Rueff, S. Agrestini, Y. Utsumi, K.D. Tsuei, Y.F. Liao, F. Borgatti, G. Panaccione, A. Regoutz, R. G. Egdell, B.J. Morgan, D.O. Scanlon, D.J. Payne Physical Review Letters 112 117601 (2014). 6 Role of spin -orbit coupling in the electronic structure of IrO 2. P.K. Das, J. Slawinska, I. Vobornik, J. Fujii, A. Regoutz, J.M. Kahk, D.O. Scanlon, B.J. Morgan, C. McGuinness, E. Plekhanov, D. Di Sante, Y. -S. Huang, R. -S. Chen, G. Rossi, S. Picozzi, W.R. Branford, G. Panaccione, D.J. Payne, Physical Review Materials , 2, 065001 (2018). 7 Insights into the electronic structure of OsO 2 using soft and hard x -ray photoelectron spectroscopy in combination with density functional theory . A. Regoutz, A.M. Ganose, L. Blumenthal, C. Schlueter, T. -L. Lee, G. Kieslich, A.K. Cheetham, G. Kerherve, Y. -S. Huang, R. -S. Chen, G.M. Vinai, T. Pincelli, G. Panaccione, K.H.L. Zhang, R.G. Egdell, J. Lischner, D.O. Scanlon, D.J. Payne, Physical Review Materials , 3, 025001 (2019). Download PDF
On: February 12, 2020 From: 14h00 To: 15h00View talk
Physics and Astronomy Colloquia
Speaker: Zoe Leinhardt (University of Bristol)
Extrasolar planets are a diverse population along all dimensions from individual physical characteristics such as mass and mean density to the dynamical characteristics of the planetary system such as semi-major axis and number of planets. The ease with which extrasolar planets seem to form has resulted in discoveries of planets around unlikely host stars such as tight binaries and evolved post main sequence remnant stellar cores. In order to understand the diversity of the extrasolar planet population we need to understand planet formation in detail. However, most of the process is difficult to observe directly. In this talk I will review numerical results of planetary evolution and also highlight a few particularly interesting observations of potentially extreme events from violent collisions to the death of a solar system that may help tie our theoretical evolution models to reality.
On: February 14, 2020 From: 10h00 To: 11h00View talk
Speaker: PhD students ()
13:00-13:15 OGUGU, Edward, "Enhanced Detection of Improvised Explosive Devices (IEDs) using Nanophotonics" 13:15-13:30 TITZE, Vera, "Time-Domain Spectroscopy for High Throughput Biolaser Sensing" 13:30- 13:45 XIAO, Jianling, “Holographic metasurfaces"
13:45-14:00 COWIE, Ross, “TBC".
On: February 18, 2020 From: 13h00 To: 14h00View talk
Speaker: Prof Beatriz Roldan Cuenya (Fritz Haber Institute of the Max Planck Society)
Insight into CO 2 Electroreduction through rational Catalyst and Electrolyte Design
Beatriz Roldan Cuenya
Department of Interface Science, Fritz -Haber -Institute of the Max Planck Society , 14195 Berlin Germany
T he utilization of fossil fuels as the main energy source gives rise to serious environmental issues, including global warming caused by the continuously increasing level of atmospheric CO 2. Recently, the electrochemical conversion of CO 2 (CO 2RR) to chemicals and fuels driven by electricity derived from renewable energy has been recognized as a promising strategy towards sustainable energy. In my talk I will provide examples of recent advances in the development of highly active plasma -modified single crystals , nanostructured thin films and nanoparti cle (NP) electrocatalysts (Cu, Ag, Zn, and Cu- M with M = Zn, Sn ) and how their structure (crystal orientation , atomic arr angement, size, shape, defects ), oxidation state and composition i nfluence the ir selectivity in CO 2RR. I will also discuss how importan t morphological motives and chemical sites can be created and re generated in pulsed electrochemistry experiments. Additionally , the determining role of the electrolyte in the surface restructuring, reaction activity and selectivity will be illustrated . Finally, the importance of in situ and operando characterization methods (e.g. EC -AFM, Liquid-TEM, XAS, XPS , XRD) to gain in depth understanding on the structure - and electrolyte -sensitivity of real CO 2RR catalysts under working conditions will be demonstr ated. Our results are expected to open up new routes for the reutilization of CO 2 through its direct selective conversion into higher value products such as ethylene and ethanol. Download PDF
On: February 26, 2020 From: 14h00 To: 15h00View talk
Speaker: Ian Ashworth ()
Why is Physical Organic Chemistry Important in Pharmaceutical Chemical Process Development? Ian W Ashworth AstraZeneca Pharmaceutical Technology & Development, Silk Road Business Park, Charter Way, Macclesfield, SK10 2NA, UK
The uti lity of applying app roaches rooted in physical organ ic chemistry to the development of manufacturing processes f or active pharmaceutical ingredients (A PIs) will be demonstrated through three AstraZeneca case studies . These will illustrate applications to a reaction, work -up a nd to contr ol a reaction occurring during the formation an d c rystallisation of a s alt.
The study of a reaction is exemplified by the investigation of the kinetics and mechanism of a Williamson style ether synthesis . The observed first order kinetics led us to the conclusion that the activation of the alkylating agent to form a reactive intermediate was the rate controlling pr ocess in th is reaction . The consequences of this conclusion in relation to our ability to contr ol the formation of alkylated impuriti es will be discussed.
The work -up phase of a reaction will be illustrated by an investigation of a pH - controlled ex traction. Unexp ectedly we found that we were able to sepa rate unreacted starting mat erial from the product of a Buchwald -Hartwig cou pling re action despite the two compounds having nearly identical p Kas. These observations led us to propose a general equation for the part ition of ionisable molecules as a function of pH and the molecules pa rtition coefficient.
Finally , the potential for chemist ry to occur during crystallisations will be discussed in the light of a fina l API salt formation in methanol. Self -cata lysed esteri fication of the salt forming acid was observed that could lead to the isolat ion of the wrong solid form of the API . Download PDF
On: March 4, 2020 From: 14h00 To: 15h00View talk
Physics and Astronomy Colloquia
Speaker: Prof Alison Walker (University of Bath)
Multiscale modeling refers to a combination of multiple models at different scales used simultaneously to describe a system. These models focus on different scales of resolution, atomistic through mesoscopic to continuum (macroscale). Combining the models allows us to understand how microscopic processes governing charge and energy transport influence behaviour, e.g. charge mobilities, at a macroscopic length scale. I will describe our use of random walk Monte Carlo models at the mesoscopic level and link the length scales. I will show how we can predict the performance of novel optoelectronic devices such as perovskite and organic solar cells and light emitting diodes. In perovskite solar cells, I will describe how our drift diffusion model of ionic-electronic conduction has shown how mobile ion vacancies cause hysteresis. I will also demonstrate predictions from a mesoscopic model in which the charge carriers are treated as polarons and that shows the conditions under which hot polarons can beat the Shockley–Queisser limit. Charge carriers in organic semiconductors in organic solar cells and in charge transport layers are also polarons. Here, polaron transport depends sensitively on molecular packing arrangements. I will describe simulation of charge and energy transport in small molecule and polymer semiconductors with a recently developed fast electrostatics solver and with morphologies obtained with the code Simulation of Atomistic Molecular Structures using an Elastic Network (SAMSEN) developed by my group . Large systems, e.g. 100 polymers each 10 monomers long, can be simulated with SAMSEN in around a day with a desktop computer.
 A R Smith, I R Thompson, A B Walker J. Chem. Phys. 150, 164115 (2019)
On: March 6, 2020 From: 10h00 To: 11h00View talk