Electronic structure of oxide fuels from experiment and first principles calculations

Aguiar, J. Albino; Grønbech‐Jensen, Niels; Perlov, A. Ya.; Milman, Victor; Gao, Shang; Pickard, Chris J.; Browning, Nigel D.

doi:10.1088/1742-6596/241/1/012062

Cited by 5 publications

(7 citation statements)

References 5 publications

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“…The scalar relativistic corrections were found to be important for core (non-valence) electrons; therefore, scalar relativistic atomic calculations are used only for the generation of both norm-conserving (NCP) and ultrasoft pseudopotentials (USPs). It has also been demonstrated that the energy loss spectra from a variety of cubic oxides (including urania) are in qualitative agreement with the results of CASTEP calculations [18].…”

Section: Structure Of (U Th Pu) Oxidessupporting

confidence: 72%

Application of density functional theory in assessing properties of thoria and recycled fuels

Szpunar¹,

Szpunar²

2013

Journal of Nuclear Materials

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Section: Structure Of (U Th Pu) Oxidessupporting

confidence: 72%

Application of density functional theory in assessing properties of thoria and recycled fuels

Szpunar¹,

Szpunar²

2013

Journal of Nuclear Materials

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“…Comparison of the top three spectra in Figure 10 can attest to the importance of Hubbard U in XAS simulation of STCH materials. The two plots at the bottom of Figure 10, both of which are obtained using the same Hubbard parameter (U = 5.4 eV), show a severe underestimation of the pre-peak height in the single-particle FCH treatment when compared to the MBXAS spectrum, which is in good agreement with the experimental results (Aguiar et al, 2010). This underestimation is reported for oxides of a large number of transition metals and can be explained with the help of a simple tight-binding model (Liang and Prendergast, 2018).…”

Section: Frontiers In Energy Researchsupporting

confidence: 79%

Synchrotron-based techniques for characterizing STCH water-splitting materials

et al. 2022

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Understanding the role of oxygen vacancy–induced atomic and electronic structural changes to complex metal oxides during water-splitting processes is paramount to advancing the field of solar thermochemical hydrogen production (STCH). The formulation and confirmation of a mechanism for these types of chemical reactions necessitate a multifaceted experimental approach, featuring advanced structural characterization methods. Synchrotron X-ray techniques are essential to the rapidly advancing field of STCH in part due to properties such as high brilliance, high coherence, and variable energy that provide sensitivity, resolution, and rapid data acquisition times required for the characterization of complex metal oxides during water-splitting cycles. X-ray diffraction (XRD) is commonly used for determining the structures and phase purity of new materials synthesized by solid-state techniques and monitoring the structural integrity of oxides during water-splitting processes (e.g., oxygen vacancy–induced lattice expansion). X-ray absorption spectroscopy (XAS) is an element-specific technique and is sensitive to local atomic and electronic changes encountered around metal coordination centers during redox. While in operando measurements are desirable, the experimental conditions required for such measurements (high temperatures, controlled oxygen partial pressures, and H2O) practically necessitate in situ measurements that do not meet all operating conditions or ex situ measurements. Here, we highlight the application of synchrotron X-ray scattering and spectroscopic techniques using both in situ and ex situ measurements, emphasizing the advantages and limitations of each method as they relate to water-splitting processes. The best practices are discussed for preparing quenched states of reduction and performing synchrotron measurements, which focus on XRD and XAS at soft (e.g., oxygen K-edge, transition metal L-edges, and lanthanide M-edges) and hard (e.g., transition metal K-edges and lanthanide L-edges) X-ray energies. The X-ray absorption spectra of these complex oxides are a convolution of multiple contributions with accurate interpretation being contingent on computational methods. The state-of-the-art methods are discussed that enable peak positions and intensities to be related to material electronic and structural properties. Through careful experimental design, these studies can elucidate complex structure–property relationships as they pertain to nonstoichiometric water splitting. A survey of modern approaches for the evaluation of water-splitting materials at synchrotron sources under various experimental conditions is provided, and available software for data analysis is discussed.

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“…In contrast to ZrO 2 and CeO 2 , UO 2 is incorrectly predicted to be a metal by DFT, and in order to correctly model the electronic structure it is necessary to use methods beyond DFT, such as DFT + U or hybrid functionals [13]. In the current work, we extend previous investigations that have compared measured and calculated EEL spectra by considering the role of experimental broadening on the calculated oxygen K-edge energy loss near edge structure (ELNES), which has not been taken into account previously in the literature, to the best of our knowledge [14]. This additional parameter allows us to closely match our spectral simulations to experimental spectra both qualitatively and quantitatively using non-linear least squares (NLLS) peak fitting and statistical analysis.…”

Section: Introductionmentioning

confidence: 91%

Investigating the electronic structure of fluorite-structured oxide compounds: comparison of experimental EELS with first principles calculations

Aguiar¹,

Ramasse²,

Asta³

et al. 2012

J. Phys.: Condens. Matter

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Energy loss spectra from fluorite-structured ZrO(2), CeO(2), and UO(2) compounds are compared with theoretical calculations based on density functional theory (DFT) and its extensions, including the use of Hubbard-U corrections (DFT + U) and hybrid functionals. Electron energy loss spectra (EELS) were obtained from each oxide using a scanning transmission electron microscope (STEM). The same spectra were computed within the framework of the full-potential linear augmented plane-wave (FLAPW) method. The theoretical and experimental EEL spectra are compared quantitatively using non-linear least squares peak fitting and a cross-correlation approach, with the best level of agreement between experiment and theory being obtained using the DFT + U and hybrid computational approaches.

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Electronic structure of oxide fuels from experiment and first principles calculations

Cited by 5 publications

References 5 publications

Application of density functional theory in assessing properties of thoria and recycled fuels

Application of density functional theory in assessing properties of thoria and recycled fuels

Synchrotron-based techniques for characterizing STCH water-splitting materials

Investigating the electronic structure of fluorite-structured oxide compounds: comparison of experimental EELS with first principles calculations

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