The third of these online meetings will be based around the Chemistry and Catalysis session that would have taken place at NMSUM. This will take place on the afternoon of Wed 7 October 2020, and an outline programme is below. The programme includes talks by the winners of the ISIS Impact Awards this year.
If you would like to attend the webinar, please use this link to register online. There is no charge for the meeting; registering will allow us to send you a Zoom link for the meeting nearer the time.
13.40 Paul Gratrex (KTH Royal Institute of Technology, Sweden) - Bond
hybridisation within interconnected lignin-derived non-graphitisable carbon
Current models of non-graphitisable carbon (NGC) describe a two-phase system in which graphitic nanocrystals are linked and contained by amorphous carbon. Such models assume a mix of sp2 and sp3 hybridised regions. Since it is tricky to directly observe the hybridisation of carbon, we use the hybridisation of terminal carbon/hydrogen bonds as an approximation of the bulk, which can be conveniently measured by the C-H stretch energy using inelastic neutron scattering (INS). We find that NGCs manufactured above 800°C contain next to no sp3 C-H groups, and thus conclude that NGCs are almost purely sp2 hybridised carbon. Moreover, the terminal proton concentration approaches zero above 1200°C, from which we conclude that the carbon is largely interconnected, without 'edges'. Interestingly, measurements of NGCs manufactured at temperatures as high as 2500°C reveal water trapped inside NGCs.
14.00 Monica Jimenez-Ruiz (ILL) - Inelastic Neutron Scattering Study of Brønsted acidity and proton transfer in zeolites
Zeolites, crystalline and microporous aluminosilicates, are one of the most important groups of functional materials. Zeolites can be described as microcoporous polymorphs of quartz. Whilst quartz is SiO2, zeolites asmit the isomorphous substitution of Si by many tetrahedrally coordinated atom, typically Al (Si4+ à Al3+ + H+). In this way, the Si/Al ratio gives the number of acid sites, but not their location and strength. Inelastic neutron scattering (INS) has been used to study the acid sites of the LTA zeolite with different Si/Al ratios. The combination of an extremely high quality of the samples and the sensitivity of the instrument allows to detect with high precision the acid sites of LTA and obtain information about its position. In order to fully understand the INS spectra we performed ab-initio calculations [1,2]. In addition the polar properties of zeolites can be nicely tuned by selecting the appropriate chemical composition and concentration of structural defects in their frameworks. In the present study we were particularly interested about the mechanism of water adsorption on small pore zeolites and the influence of the water clustering on the hydroxonium formation. The simple framework of the chabazite makes this zeolite and ideal candidate for the this study combining INS measurements and Ab-initio Molecular Dynamics Simulations .
References:  T. Lemishko et al., J. Phys. Chem. C 2016, 120, 24904−24909.  T. Lemishko et al., J. Phys. Chem. C 2018, 122, 11450−11454 .  M. Jimémez-Ruiz et al., J. Phys. Chem. C 2020, 124, 5436−5443.
14.20 Sumit Konar (Edinburgh) - Pressure-induced crystallisation of Para-xylene
Liquids usually crystallize at a defined pressure. Pressure-induced
crystallization of liquid offers an alternative strategy to crystallization at
low temperature. We investigated pressure-induced crystallisation on
para-xylene which is a raw material in the large-scale synthesis of
various polymers, including polyethylene terephthalate. A hydrostatic
compression using Neutron powder diffraction, was conducted in a
Paris-Edinburgh apparatus on perdeuterated p-xylene (C8D10) in the pressure
range 0 – 5 GPa. Isothermal equation of state was obtained, and the
high-pressure response of these materials is supported by dispersion-corrected
DFT calculations which, while overestimating the experimental bulk moduli
values, give excellent agreement with the observed smooth compression response.
To rule out the deutearion effect, hydrogenated p-xylene (C8H10) was also
compressed above the freezing pressure of the liquid and single crystals were
grown inside a diamond anvil cell (DAC) at around 0.2 GPa. The crystals were
sufficiently large and thus allowing the structure to be solved at high
pressure. Para-xylene crystallises in a monoclinic space group P21/n,
a = 5.6517(10), b = 4.9382(8), c=10.867(4) Å, b = 100.436(19) ͦ , and V =
298.272 Å3. The crystal structure resembles with the previously determined low
temperature crystal structure of p-xylene at ambient pressure.
14.50 Paolo Rech (Federal University of Rio Grande do Sul, Brazil) - Are Self-Driving Cars Reliable? Evaluation of Radiation-Induced Errors in Automotive Applications
The new trend in the automotive market is self-driving system. To be implemented, a self-driving platform needs to be able to analyze a huge amount of images and signals in real time. This is achieved thanks to Convolutional Neural Networks (CNNs) executed on Graphics Processing Units (GPUs). The Tesla self-driving system, for instance, is powered by NVIDIA embedded GPUs executing CNNs-based object-detection. GPUs were originally designed for multimedia applications, for which reliability is not an issue. Their architecture is then optimized to increase performances, not reliability. In the talk we will discuss the reliability of GPUs and evaluate if they are compliant with the strict ISO 26262, which is the standard that define the reliability constraints for automotive applications. The talk will focus on the reliability of object-detection algorithm and convolution neutral networks (including YOLO, Faster RCNN, and ResNet).We will understand how to identify radiation-induced errors in GPUs and distinguish between tolerable errors and critical errors.
After a brief description of radiation effects at physical level we will show the real impact of neutrons in GPUs by presenting accelerated neutron beam results that correspond to more than 150,000 years of natural exposure. Our data demonstrates that most of radiation-induced errors in GPUs can be tolerated, even in safety-critical applications. We will show how to replicate the causes of critical errors through architectural-level and instruction-level fault-injection. By hardening only critical error sources, we will be able to increase the reliability of the application without unnecessary overhead.
15.10 Malcolm Levitt (Southampton) - Neutron scattering and terahertz spectroscopy of molecular endofullerenes
Molecular endofullerenes are stable chemical substances in which single molecules are fully encapsulated in symmetrical carbon cages. The encapsulated molecules are free to translate and rotate, even at cryogenic temperatures, and display quantization of their translational, rotational, and vibrational modes. In many cases they also display spin isomerism. Transitions between the quantum energy levels are observed by inelastic neutron scattering, infrared spectroscopy, terhertz spectroscopy, and nuclear magnetic resonance. I will give a brief overview of the experimental observations and the information that they provide.
15.30 Jin-Chong Tan (Oxford) - Application of inelastic neutron scattering (INS) to measure nanoporous framework dynamics
We will focus on the terahertz dynamics underpinning the functions of porous metal-organic frameworks. Vibrational modes in terahertz frequencies were measured by inelastic neutron scattering, and density functional theory (DFT) calculations were performed to explain the origin of the collective modes, such as rotor dynamics, gate opening, lattice shearing, and pore breathing. The combined experimental and theoretical results shed new light on the mechanics of nanoporous frameworks, their complex elasticity and dynamics that control structural stability and stimuli-responsive behaviour.
15.50 Peter Albers (Evonik) - Characterisation of hydrogenous species on/in unsupported and supported Pd and Pt catalysts applied in industry; Or: Synergies between fundamental hydrogen in metals research and chemical engineering.