Publications
497 results found
Riveros M, Guo M, van dam, et al., 2017, Carbon Arbitrage with Stationary Batteries in the City of London, 27th European Symposium on Computer Aided Process Engineering, Publisher: Elsevier, Pages: 529-534, ISSN: 1570-7946
Stationary batteries could facilitate provision of carbon arbitrage services in cities. Such services offer a smart solution to integrate low-carbon energy technology into grid electricity supply and help tackle climate change. In this paper the environmental implications and overall profitability of this approach are assessed. A modelling framework has been developed to design an energy storage system with optimal capacity to maximise carbon savings. The City of London was used as a case study to demonstrate model applicability and analyse the potential effect of intermittent renewable energy sources in the supply system. The total savings obtained for the carbon arbitrage service were economically valorised using carbon market prices. In addition, a critical profitability thresholds for carbon trading prices are identified. Results show that this approach could bring environmental benefits depending on the carbon intensity of the grid, but that high carbon trading prices are required before it is economically feasible.
Cooper SJ, Bertei A, Finegan DP, et al., 2017, Simulated impedance of diffusion in porous media, Electrochimica Acta, Vol: 251, Pages: 681-689, ISSN: 0013-4686
This paper describes the use of a frequency domain, finite-difference scheme to simulate the impedance spectra of diffusion in porous microstructures. Both open and closed systems are investigated for a range of ideal geometries, as well as some randomly generated synthetic volumes and tomographically derived microstructural data. In many cases, the spectra deviate significantly from the conventional Warburg-type elements typically used to represent diffusion in equivalent circuit analysis. A key finding is that certain microstructures show multiple peaks in the complex plane, which may be misinterpreted as separate electrochemical processes in real impedance data. This is relevant to battery electrode design as the techniques for nano-scale fabrication become more widespread. This simulation tool is provided as an open-source MatLab application and is freely available online as part of the TauFactor platform.
Jing R, Wang M, Brandon N, et al., 2017, Multi-criteria evaluation of solid oxide fuel cell based combined cooling heating and power (SOFC-CCHP) applications for public buildings in China, Energy, Vol: 141, Pages: 273-289, ISSN: 0360-5442
This study aims to evaluate the feasibility of solid oxide fuel cell based combined cooling heating and power (SOFC-CCHP) applications in public buildings of China from different perspectives. Operations of the natural gas fueled SOFC-CCHP systems for 20 years’ have been simulated for five categories of public buildings in five locations of China. Parallel simulations of combustion based CCHP systems and conventional system have been conducted for comparison. By single criterion assessment, SOFC-CCHP systems demonstrate outstanding performance on energy efficiency as well as reducing carbon emission, air pollution and human health damage cost. The levelized cost of energy (LCOE) turns out to be competitive with commercial electricity price, but a long payback period (SPP) has also been identified. To further assess the overall performance of SOFC-CCHP systems, a multi-criteria assessment model has been developed by combining the gray relational analysis (GRA) approach and the entropy-weighting method. The result indicates that hospital, hotel, and supermarket achieve more benefits than office and school; warmer regions rank slightly higher than colder regions. In addition, sensitivity analysis has been performed on SPP and LCOE. Overall, this paper provides theoretical guidance and evaluation approach for SOFC-CCHP demonstrations in China.
Biton M, Tariq F, Yufit V, et al., 2017, Integrating multi-length scale high resolution 3D imaging and modelling in the characterisation and identification of mechanical failure sites in electrochemical dendrites, Acta Materialia, Vol: 141, Pages: 39-46, ISSN: 1359-6454
The Zn-air battery system is attractive because of its potentially high power density, environmental compatibility and low-cost materials [1]. This paper is focused on understanding the degradation of Zn air batteries, in particular the evolution of Zn dendrites, one of the main degradation mechanisms. Complementary tomographic techniques allow the direct 3D imaging and characterisation of complex microstructures, including the observation and quantification of dendrite growth. Here we present results from 3D x-ray and FIB-SEM tomography of Zn dendrite formation in a zinc-air battery, down to resolutions of tens of nanometers, enabling analysis of complex micro-structures. This approach is shown to be effective in understanding how electrochemical dendrites grow, and demonstrates that tomography coupled with modelling can provide new insights into dendrite growth in electrochemical systems.
Chen X, Liu X, Childs P, et al., 2017, A low cost desktop electrochemical metal 3D printer, Advanced Materials Technologies, Vol: 2, ISSN: 2365-709X
Additive manufacturing (AM), or 3D printing as it is more commonly known, is the process of creating 3D objects from digital models through the sequential deposition of material in layers. Electrochemical 3D printing is a relatively new form of AM that creates metallic structures through electrochemical reduction of metal ions from solutions onto conductive substrates. The advantage of this process is that a wide range of materials and alloys can be deposited under ambient conditions without thermal damage and more importantly at low cost, as this does not require expensive laser optics or inert gas environments. Other advantages include the fact that this process can be both additive and subtractive through reversal of potential allowing for recycling of components through electrochemical dissolution. However, one main limitation of this technology is speed. Here, a novel electrochemical 3D printer design is proposed using a meniscus confinement approach which demonstrates deposition rates three orders of magnitude higher than equivalent systems due to improved mass transport characteristics afforded through a mechanical electrolyte entrainment mechanism. Printed copper structures exhibit a polycrystalline nature, with decreasing the grain size as the potential is increased resulting in a higher Vickers hardness and electronic resistivity.
Brandon N, Hagen A, Dawson R, et al., 2017, “Solid Oxide Fuel Cells, Electrolyzers and Reactors: From Development to Delivery – EFCF2016”, Fuel Cells, Vol: 17, Pages: 414-414, ISSN: 1615-6846
Somalu MR, Muchtar A, Daud WRW, et al., 2017, Screen-printing inks for the fabrication of solid oxide fuel cell films: A review, RENEWABLE & SUSTAINABLE ENERGY REVIEWS, Vol: 75, Pages: 426-439, ISSN: 1364-0321
Speirs J, Balcombe P, Johnson E, et al., 2017, A Greener Gas Grid: What Are the Options?, A greener gas grid: what are the options?
Chen J, Bertei A, Ruiz-Trejo E, et al., 2017, Characterization of Degradation in Nickel Impregnated Scandia-Stabilize Zirconia Electrodes during Isothermal Annealing, Journal of The Electrochemical Society, Vol: 164, Pages: F935-F943, ISSN: 1945-7111
This study investigates the stability of nickel-impregnated scandia-stabilize zirconia composite electrodes during isothermal annealing at temperatures from 600 to 950°C in a humidified hydrogen atmosphere (3 vol % water vapor). Typically an initial rapid degradation of the electrode during the first 17 h of annealing is revealed by both an increase in polarization resistance and a fall in electronic conductivity. Secondary electron images show a shift in nickel particle size toward larger values after 50 h of annealing. The declining electrochemical performance is hence attributed to nickel coarsening at elevated temperatures. Nickel coarsening has two microstructural effects: breaking up nickel percolation; and reducing the density of triple phase boundaries. Their impact on electrode area specific resistance is explored using a physical model of electrode performance which relates the macroscopic electrochemical performance to measurable microstructural parameters.
Ruiz-Trejo E, Bertei A, Maserati A, et al., 2017, Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites, Journal of The Electrochemical Society, Vol: 164, Pages: F3045-F3054, ISSN: 1945-7111
Dense composites of silver and Sc-stabilized ZrO2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens’ reagent. A composite with 8.6 vol % of silver exhibits metallic conductivity of 186 S cm−1 and oxygen flux of 0.014 μmol cm−2 s−1 at 600°C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample (Ag 4.7 vol%) is analyzed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and Ag, yet small silver particles on the surface improve the reduction of oxygen. Oxygen reduction is highly promoted by silver on the surface and there are no limitations of charge transfer at the interface between silver and ScSZ.
Bertei A, Ruiz Trejo E, Kareh K, et al., 2017, The fractal nature of the three-phase boundary: A heuristic approach to the degradation of nanostructured solid oxide fuel cell anodes, Nano Energy, Vol: 38, Pages: 526-536, ISSN: 2211-2855
Nickel/zirconia-based nanostructured electrodes for solid oxide fuel cells suffer from poor stability even at intermediate temperature. This study quantifies the electrochemical and microstructural degradation of nanostructured electrodes by combining 3D tomography, electrochemical impedance spectroscopy (EIS) and mechanistic modeling. For the first time, the electrochemical degradation of nanostructured electrodes is quantified according to the fractal nature of the three-phase boundary (TPB). Using this hypothesis an excellent match between modeling and the electrochemical response is found. The origin of the degradation in microstructure and electrochemical performance can be found in the initial fractal roughness of the TPB at a length scale not detectable with state-of-the-art tomography at 30 nm resolution. This additionally implies that the hydrogen electro-oxidation takes place within 4 nm from the geometric TPB line, revealing that the electrochemical reaction zone cannot be regarded anymore as a one-dimensional line when dealing with nanoparticles.
Chen YA, Ji L, Brandon N, et al., 2017, A study on the flow field design of lead flow batteries, 10th International Conference on Lead-Acid Batteries, LABAT 2017, Pages: 199-200
Xie M, Chen Y, Li X, et al., 2017, Influences of surfactant additives on performances of lead acid flow batteries, 10th International Conference on Lead-Acid Batteries, LABAT 2017, Pages: 121-122
Brandon NP, Kurban Z, 2017, Clean energy and the hydrogen economy, Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 375, ISSN: 1364-503X
In recent years, new-found interest in the hydrogeneconomy from both industry and academia hashelped to shed light on its potential. Hydrogencan enable an energy revolution by providing muchneeded flexibility in renewable energy systems. Asa clean energy carrier, hydrogen offers a rangeof benefits for simultaneously decarbonizing thetransport, residential, commercial and industrialsectors. Hydrogen is shown here to have synergieswith other low-carbon alternatives, and can enablea more cost-effective transition to de-carbonizedand cleaner energy systems. This paper presentsthe opportunities for the use of hydrogen in keysectors of the economy and identifies the benefitsand challenges within the hydrogen supply chain forpower-to-gas, power-to-power and gas-to-gas supplypathways. While industry players have alreadystarted the market introduction of hydrogen fuelcell systems, including fuel cell electric vehicles andmicro-combined heat and power devices, the use ofhydrogen at grid scale requires the challenges of cleanhydrogen production, bulk storage and distribution tobe resolved. Ultimately, greater government support,in partnership with industry and academia, is stillneeded to realize hydrogen’s potential across alleconomic sectors.
Chen Z, Wang X, Brandon N, et al., 2017, Spherical indentation of bilayer ceramic structures: dense layer on porous substrate, Journal of the European Ceramic Society, Vol: 37, Pages: 4763-4772, ISSN: 1873-619X
Spherical indentation of thin 8YSZ ceramic layers on porous substrates (NiO/Ni-8YSZ) was studied. Indentation-induced elastic and plastic deformation and damage of the bilayer was experimentally analysed. FE simulations of the indentation process were carried out using the Gurson model to account for densification of the porous substrates. The simulated load-depth responses were in excellent agreement with the measured ones. The resulting stress distributions showed that the damage to the YSZ initiates in a tensile region near the interface due to bending during loading at a failure stress of ∼2 GPa, which is consistent with pores of ∼1 μm size seen in the YSZ. Delamination occurs on unloading due to the elastic recovery of YSZ being greater than that of the substrates at a de-bonding stress of 120 MPa. Residual compressive stress in the YSZ inhibits crack opening displacements normal to the layer plane which is beneficial for application of these structures in SOFCs.
Ouyang M, Boldrin P, Brandon NP, 2017, Methane Pulse Study on Nickel Impregnated Gadolinium Doped Ceria, 15th International Symposium on Solid Oxide Fuel Cells (SOFC), Publisher: ELECTROCHEMICAL SOC INC, Pages: 1353-1366, ISSN: 1938-5862
Cooper SJ, brandon NP, 2017, Solid Oxide Fuel Cell Lifetime and Reliability, Solid Oxide Fuel Cell Lifetime and Reliability Critical Challenges in Fuel Cells, Editors: Ruiz-Trejo, BOLDRIN, Publisher: Academic Press, Pages: 1-15, ISBN: 9780128097243
For its holistic approach, this book can be used both as an introduction to these issues and a reference resource for all involved in research and application of solid oxide fuel cells, especially those developing understanding in ...
Jais AA, Ali SAM, Anwar M, et al., 2017, Enhanced ionic conductivity of scandia-ceria-stabilized-zirconia (10Sc1CeSZ) electrolyte synthesized by the microwave-assisted glycine nitrate process, Ceramics International, Vol: 43, Pages: 8119-8125, ISSN: 0272-8842
Scandia-stabilized-zirconia is a potential zirconia-based electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, the properties of zirconia co-doped with 10 mol% Sc and 1 mol% Ce (scandia-ceria-stabilized-zirconia, 10Sc1CeSZ) electrolyte synthesized by the microwave-assisted glycine nitrate process (MW-GNP) were determined. The effects of microwave heating on the sintering temperature, microstructure, densification and ionic conductivity of the 10Sc1CeSZ electrolyte were evaluated. The phase identification, microstructure and specific surface area of the prepared powder were investigated using X-ray diffraction, transmission electron microscopy and the Brunauer-Emmett-Teller technique, respectively. Using microwave heating, a single cubic-phase powder was produced with nanosized crystallites (19.2 nm) and a high specific surface area (16 m2/g). It was found that the relative density, porosity and total ionic conductivity of the 10Sc1CeSZ electrolyte are remarkably influenced by the powder processing method and the sintering temperature. The pellet sintered at 1400 °C exhibited a maximum ionic conductivity of 0.184 S/cm at 800 °C. This is the highest conductivity value of a scandia-stabilized-zirconia based electrolyte reported in the literature for this electrolyte type. The corresponding value of the activation energy of electrical conductivity was found to be 0.94 eV in the temperature range of 500–800 °C. Overall, the use of microwave heating has successfully improved the properties of the 10Sc1CeSZ electrolyte for application in an IT-SOFC.
Ouyang M, Boldrin P, Brandon NP, 2017, Methane Pulse Study on Nickel Impregnated Gadolinium Doped Ceria, 12th European SOFC & SOE Forum
Somalu MR, Muchtar A, Brandon NP, 2017, Properties of screen-printed nickel/scandia-stabilized-zirconia anodes fabricated using rheologically optimized inks during redox cycles, JOURNAL OF MATERIALS SCIENCE, Vol: 52, Pages: 7175-7185, ISSN: 0022-2461
Jamil Z, Ruiz-Trejo E, Brandon NP, 2017, Nickel Electrodeposition on Silver for the Development of Solid Oxide Fuel Cell Anodes and Catalytic Membranes, Journal of The Electrochemical Society, Vol: 164, Pages: D210-D217, ISSN: 1945-7111
Nickel was electrodeposited on porous Ag/GDC (silver/Ce0.9Gd0.1O2-x) scaffolds and dense Ag/GDC composites for the fabricationof SOFC electrodes and catalytic membranes respectively. To control the distribution and amount of nickel deposition on the Ag/GDCsurfaces; first, a systematic cyclic voltammetry study of nickel electrodeposition from a Watts bath on silver foils was carried outto understand the influence of operating conditions on the electrodeposition process. From the cyclic voltammetry study, it can beconcluded that suitable operating conditions for nickel electrodeposition into porous Ag/GDC scaffolds and catalytic membranesare: 1.1 M Ni2+ concentration in Watts bath; deposition potential between −0.65 to −1.0 V vs. Ag/AgCl; a temperature at 55◦C;sodium dodecyl sulfate (SDS) as the surfactant; pH 4.0 ± 0.2 and an agitation rate of 500 rpm. It was observed that the nickel surfacemicrostructure changed with the deposition current densities due to the co-evolution of H2. Pulse and continuous electrodepositionmodes allow nickel to be deposited throughout porous Ag/GDC scaffolds and onto catalytic membranes. The pulse electrodepositionmode is favored as this is shown to result in an even Ni distribution within the porous scaffolds at minimum H2 pitting.
Chen Z, Atkinson A, Brandon N, 2017, Characterization of deformation and damage in porous sofc components via spherical indentation and simulation, 40th International Conference on Advanced Ceramics and Composites, Pages: 143-157
© 2018 by World Scientific Publishing Europe Ltd. The aim of this work is to present the methodology to characterize deformation and contact damage initiation and evolution in porous bulk and film components used in solid oxide fuel cells, based on indentation and simulation. Spherical indentation tests at a broad range of loads (50-10000 mN) were carried out on porous bulk and film electrodes with different levels of porosity, and on bilayer system. An axisymmetric model based on the Gurson model used for porous materials was developed to simulate the indentation processes. Elasticity and hardness of each component were reliably determined via both experiments and modelling. Inverse analysis via comparison of experimental indentation response curves and simulation-generated curves shows a very different relation between hardness and yield stress, compared with dense materials. Cracking behaviour was examined and appropriately explained by FEM results. Further insight of the deformation and damage behaviour was also obtained based on microstructural study using FIB-SEM. Overall, the study shows that the model developed in this work is highly applicable for the description the deformation and damage characteristics in porous bulk and film ceramics.
Brandon NP, Ruiz-Trejo E, Boldrin P, 2017, Solid Oxide Fuel Cell Lifetime and Reliability: Critical Challenges in Fuel Cells, ISBN: 9780081011027
Solid Oxide Fuel Cell Lifetime and Reliability: Critical Challenges in Fuel Cells presents in one volume the most recent research that aims at solving key issues for the deployment of SOFC at a commercial scale and for a wider range of applications. To achieve that, authors from different regions and backgrounds address topics such as electrolytes, contaminants, redox cycling, gas-tight seals, and electrode microstructure. Lifetime issues for particular elements of the fuel cells, like cathodes, interconnects, and fuel processors, are covered as well as new materials. They also examine the balance of SOFC plants, correlations between structure and electrochemical performance, methods for analysis of performance and degradation assessment, and computational and statistical approaches to quantify degradation. For its holistic approach, this book can be used both as an introduction to these issues and a reference resource for all involved in research and application of solid oxide fuel cells, especially those developing understanding in industrial applications of the lifetime issues. This includes researchers in academia and industrial R&D, graduate students and professionals in energy engineering, electrochemistry, and materials sciences for energy applications. It might also be of particular interest to analysts who are looking into integrating SOFCs into energy systems. Brings together in a single volume leading research and expert thinking around the broad topic of SOFC lifetime and durability. Explores issues that affect solid oxide fuel cells elements, materials, and systems with a holistic approach. Provides a practical reference for overcoming some of the common failure mechanisms of SOFCs. Features coverage of integrating SOFCs into energy systems.
Chen J, Ruiz-Trejo E, Atkinson A, et al., 2017, Microstructural and Electrochemical Characterisation of Degradation in Nickel Impregnated Scandia-stabilised Zirconia Electrode during Isothermal Annealing, 15th International Symposium on Solid Oxide Fuel Cells (SOFC), Publisher: ELECTROCHEMICAL SOC INC, Pages: 1125-1137, ISSN: 1938-5862
Hack J, Meyer Q, Iacoviello F, et al., 2017, A MULTI-SCALE APPROACH TO POLYMER ELECTROLYTE FUEL CELL CHARACTERISATION, Pages: 235-236
Due to the complex, hierarchical structure of the materials in polymer electrolyte fuel cells (PEFC), a multilength scale approach to their characterisation has been adopted. Electrochemical characterisation techniques have become relatively standard, but the use of X-ray computed tomography (X-ray CT) for 3-dimensional, non-destructive visualisation of PEFCs is an emerging field. The use of a suite of X-ray CT instruments has allowed for a full characterisation of the fuel cell components, from the stack level to the catalyst layer. The breadth of information that can be gained using X-ray imaging techniques will allow for further development of materials and fabrication techniques.
Mukerjee S, Leah R, Selby M, et al., 2017, Life and Reliability of Solid Oxide Fuel Cell-Based Products: A Review, SOLID OXIDE FUEL CELL LIFETIME AND RELIABILITY: CRITICAL CHALLENGES IN FUEL CELLS, Editors: Brandon, RuizTrejo, Boldrin, Publisher: ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD, Pages: 173-191, ISBN: 978-0-08-101102-7
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Cooper SJ, Brandon NP, 2017, An Introduction to Solid Oxide Fuel Cell Materials, Technology and Applications, Publisher: ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD, ISBN: 978-0-08-101102-7
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Tariq F, Ruiz-Trejo E, Bertei A, et al., 2017, Microstructural Degradation: Mechanisms, Quantification, Modeling and Design Strategies to Enhance the Durability of Solid Oxide Fuel Cell Electrodes, SOLID OXIDE FUEL CELL LIFETIME AND RELIABILITY: CRITICAL CHALLENGES IN FUEL CELLS, Editors: Brandon, RuizTrejo, Boldrin, Publisher: ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD, Pages: 79-99, ISBN: 978-0-08-101102-7
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Bertei A, Tariq F, Yufit V, et al., 2016, Guidelines for the rational design and engineering of 3D manufactured solid oxide fuel cell composite electrodes, Journal of the Electrochemical Society, Vol: 164, Pages: F89-F98, ISSN: 0013-4651
The growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cells(SOFCs) with improved power density and lifetime. This technique can introduce structural modifications at a scale larger than particle size but smaller than cell size, such as by insertingelectrolyte pillars of ~5-100 µm. This study sets the minimum requirements for the rational design of 3D printedelectrodes based on an electrochemical model and analytical solutions for functional layers with negligible electronic resistanceand no mixed conduction. Results show that this structural modification enhances the power density when the ratio keffbetween effective conductivity and bulk conductivity of the ionic phase is smaller than 0.5. The maximum performance improvement is predicted as a function of keff. A design study on a wide range of pillar shapes indicates that improvements are achieved by any structural modification which provides ionic conduction up to a characteristic thickness ~10-40 µm without removing active volume at the electrolyte interface. The best performance is reached for thin (< ~2 µm) and long (> ~80 µm) pillars when the compositeelectrode is optimised for maximum three-phase boundarydensity, pointing towards the design of scaffolds with well-defined geometry and fractal structures.
Parkes MA, Tompsett DA, d'Avezac M, et al., 2016, The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study., Physical Chemistry Chemical Physics, Vol: 18, Pages: 31277-31285, ISSN: 1463-9084
Yttria stabilized zirconia (YSZ) is an important oxide ion conductor used in solid oxide fuel cells, oxygen sensing devices, and for oxygen separation. Doping pure zirconia (ZrO2) with yttria (Y2O3) stabilizes the cubic structure against phonon induced distortions and this facilitates high oxide ion conductivity. The local atomic structure of the dopant is, however, not fully understood. X-ray and neutron diffraction experiments have established that, for dopant concentrations below 40 mol% Y2O3, no long range order is established. A variety of local structures have been suggested on the basis of theoretical and computational models of dopant energetics. These studies have been restricted by the difficulty of establishing force field models with predictive accuracy or exploring the large space of dopant configurations with first principles theory. In the current study a comprehensive search for all symmetry independent configurations (2857 candidates) is performed for 6.7 mol% YSZ modelled in a 2 × 2 × 2 periodic supercell using gradient corrected density functional theory. The lowest energy dopant structures are found to have oxygen vacancy pairs preferentially aligned along the ⟨210⟩ crystallographic direction in contrast to previous results which have suggested that orientation along the ⟨111⟩ orientation is favourable. Analysis of the defect structures suggests that the Y(3+)-Ovac interatomic separation is an important parameter for determining the relative configurational energies. Current force field models are found to be poor predictors of the lowest energy structures. It is suggested that the energies from a simple point charge model evaluated at unrelaxed geometries is actually a better descriptor of the energy ordering of dopant structures. Using these observations a pragmatic procedure for identifying low energy structures in more complicated material models is suggested. Calculation of the oxygen vacancy migration activat
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