Near-edge Spectra Research Articles

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Summary Highly crystalline and emissive carbon dots (CDs) are firstly synthesized via an ionothermal method in organic solvents. In contrast to well-established approaches, ZnCl2 is utilized as the pyrolysis-promoting agent to prepare emissive CDs with tunable wavelengths, directly by carbonization from different O and N precursors under a mild reaction condition at 210°C. More than 50% synthetic yield and 39% photoluminescent quantum yield (blue CD) are obtained. XAFS measurements, in conjunction with TEM, HAADF-STEM, UPS, and ESR analyses, allow us to obtain energy diagram configuration and confirm the luminescent nature of these hard-core structured CDs. Importantly, the resulting CDs exhibit excellent capability to photogenerate superoxide radical anion (O2⋅–), which can be exemplified by both photodynamic therapy and photooxidative cyclization synthesis of tetrahydroquinolines. Representative pharmaceutical mifepristone can be derivatized in 90% yield within 10 min of irradiation of the CDs in an elegant flow reactor.

Self-magnetic-attracted NixFe(1−x)@NixFe(1−x)O nanoparticles on nickel foam as highly active and stable electrocatalysts towards alkaline oxygen evolution reaction

A facile self-magnetic-attracted approach was developed for highly active and stable NixFe(1−x)@NixFe(1−x)O/NF electrocatalysts towards alkaline oxygen evolution reaction. Firstly, a low-cost and scalable synthesis method was developed to synthesis 4–5 nm hydrophilic NixFe(1−x)@NixFe(1−x)O core–shell nanocrystals with superparamagnetism. Then, these NixFe(1−x)@NixFe(1−x)O nanoparticles (NPs) could be easily supported on nickel foam without any binders or additives. Optimized by the composition effect, the Ni0.7Fe0.3@Ni0.7Fe0.3O/NF exhibits excellent activity for oxygen evolution reaction (OER), requires only 215 mV at 10 mA·cm−2 and 260 mV at 100 mA·cm−2, with a Tafel slope of 47.4 mV·dec−1 in 1.0 M KOH. Moreover, the underlying mechanism was carefully studied by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectra (XANES) analysis and density functional theory (DFT) calculations. Due to the self-magnetic attraction, the catalyst shows outstanding stability throughout the electrocatalysis, surpassing than most self-supported catalysts. This work provides a new strategy for the construction of highly active and stable OER electrocatalysts, the nearly monodisperse magnetic NixFe(1−x)@NixFe(1−x)O NPs also serve an ideal building block for fundamental research of nickel-iron based catalyst.

X-ray absorption spectroscopy of organic sulfoxides.

Organic sulfoxides, a group of compounds containing the sulfinyl S Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O group, are widespread in nature, important in health and disease, and used in a variety of applications in the pharmaceutical industry. We have examined the sulfur K-edge X-ray absorption near-edge spectra of a range of different sulfoxides and find that their spectra are remarkably similar. Spectra show an intense absorption peak that is comprised of two transitions; a S 1s → (S–O)σ* and a S 1s → [(S–O)π* + (S–C)σ*] transition. In most cases these are sufficiently close in energy that they are not properly resolved; however for dimethylsulfoxide the separation between these transitions increases in aqueous solution due to hydrogen bonding to the sulfinyl oxygen. We also examined tetrahydrothiophene sulfoxide using both the sulfur and oxygen K-edge. This compound has a mild degree of ring strain at the sulfur atom, which changes the energies of the two transitions so that the S 1s → [(S–O)π* + (S–C)σ*] is below the S 1s → (S–O)σ*. A comparison of the oxygen K-edge X-ray absorption near-edge spectra of tetrahydrothiophene sulfoxide with that of an unhindered sulfoxide shows little change, indicating that the electronic environment of oxygen is very similar.

Li1.3Al0.3Ti1.7(PO4)3 reinforced hybrid polymer composites: assessment of enhanced Li+ ion transport and potential for solid-state supercapacitor applications

Composites of Li1.3Al0.3Ti1.7(PO4)3 (LATP) with Li+ ion containing polymer polyethylene oxide (PEO), viz. 5LiCF3SO3-95[PEO1−xLATPx], are prepared in a wide composition range (0 ≤ x ≤ 0.7). A maximum conductivity of ~ 10−4 Ω−1 cm−1 at 45 °C has been achieved for a composition x = 0.7 (70 LATP). With increase in LATP content, Li+ ion transport number systematically increases, i.e., from ~ 0.12 for 0 LATP to 0.46 for 70 LATP. Ionic mobility also exhibits a gradual rise with LATP content and attains a value ~ 2 orders of magnitude higher for 70 LATP than 0 LATP. Further, the K-edge energy of ether oxygen, obtained from X-ray absorption near-edge structure spectra, does emphasize decoupling of Li+ ions from PEO matrix, particularly for large LATP content. Our investigations suggest that such hybrid films are competitive candidates for solid ionic devices. All-solid-state supercapacitors fabricated using these films demonstrate a capacity of ~ 2–4 F-g−1.

Highly Efficient Metal-Free Nitrogen-Doped Nanocarbons with Unexpected Active Sites for Aerobic Catalytic Reactions.

Nitrogen (N)-doped nanocarbons (NDN) as metal-free catalysts have elicited considerable attention toward selective oxidation of alcohols with easily oxidizable groups to aldehydes in the past few years. However, finding a new NDN catalytic material that can meet the requirement of the feasibility on the aerobic catalytics for other complicated alcohols is a big challenge. The real active sites and the corresponding mechanisms on NDN are still unambiguous because of inevitable coexistence of diverse edge sites and N species based on recently reported doping methods. Here, four NDN catalysts with enriched pyridinic N species and without any graphitic N species are simply fabricated via a chemical-vapor-deposition-like method. The results of X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectra suggest that the dominating N species on NDN are pyridinic N. It is demonstrated that NDN catalysts perform impressive reactivity for aerobic oxidation of complicated alcohols at an atmospheric pressure. Eleven kinds of aromatic molecules with single N species and tunable π conjugation systems are used as model catalysts to experimentally identify the actual role of each N species at a real molecular level. It is suggested that pyridinic N species play an unexpected role in catalytic reactions. Neighboring carbon atoms in pyridinic N species are responsible for facilitating the rate-determining step process clarified by kinetic isotope effects, in situ nuclear magnetic resonance, in situ attenuated total reflectance infrared, and theoretical calculation. Moreover, NDN catalysts exhibit a good catalytic feasibility on the synthesis of important natural products (e.g., intermediates of vitamin E and K3) from phenol oxidation.

PyFitit: The software for quantitative analysis of XANES spectra using machine-learning algorithms

X-ray absorption near-edge spectroscopy (XANES) is becoming an extremely popular tool for material science thanks to the development of new synchrotron radiation light sources. It provides information about charge state and local geometry around atoms of interest in operando and extreme conditions. However, in contrast to X-ray diffraction, a quantitative analysis of XANES spectra is rarely performed in the research papers. The reason must be found in the larger amount of time required for the calculation of a single spectrum compared to a diffractogram. For such time-consuming calculations, in the space of several structural parameters, we developed an interpolation approach proposed originally by Smolentsev and Soldatov (2007). The current version of this software, named PyFitIt, is a major upgrade version of FitIt and it is based on machine learning algorithms. We have chosen Jupyter Notebook framework to be friendly for users and at the same time being available for remastering. The analytical work is divided into two steps. First, the series of experimental spectra are analyzed statistically and decomposed into principal components. Second, pure spectral profiles, recovered by principal components, are fitted by theoretical interpolated spectra. We implemented different schemes of choice of nodes for approximation and learning algorithms including Gradient Boosting of Random Trees, Radial Basis Functions and Neural Networks. The fitting procedure can be performed both for a XANES spectrum or for a difference spectrum, thus minimizing the systematic errors of theoretical simulations. The problem of several local minima is addressed in the framework of direct and indirect approaches. Program summaryProgram title: PyFitIt.Program Files doi:http://dx.doi.org/10.17632/ydkgfdc38t.1Licensing provisions: GNU General Public License 3.Programming language: Python, Jupyter Notebook framework.Nature of problem: Quantitative structural refinements of the X-ray absorption near-edge structure spectra (XANES). Identification of the pure spectral and concentration profiles associated with an experimental XANES dataset.Solution method: The fitting procedure of the experimental XANES spectra or of their differences is realized by means of the inverse and direct approaches based on the training set and approximation machine learning algorithms. The spectral resolution method is based on the PCA technique involving the usage of a target transformation matrix.Additional comments including restrictions and unusual features: The current version is compatible with the free FDMNES program package for XANES simulations. However, users can prepare their own matrices of spectra calculated by an arbitrary software and the corresponding structural parameters to perform the fitting procedure in PyFitIt. The complete set of examples is distributed along with the program.

Preservation of nitrogen and sulfur and passivation of heavy metals during sewage sludge composting with KH2PO4 and FeSO4

Composting is an effective method for treating sewage sludge. The aim of this work was to study preservation of nitrogen and sulfur and passivation of heavy metals during sewage sludge composting with KH2PO4 and FeSO4. The results show the loss rate of N decreased by 27.5% while that of S was increased by 32.1% compared with the control treatment during composting when KH2PO4 and FeSO4 were added. X-ray absorption near-edge structure spectra show that S was converted to a highly oxidizable state during sewage sludge composting with added KH2PO4. The mobility factors of Cu, Zn, and Pb after composting were found to decrease by 13.6%, 21.6%, and 3.8%, respectively, compared with those before composting when KH2PO4 was added. Adding these two materials to Cu and Zn inhibits Zn3(PO4)2(H2O)4 and Cu5(PO4)2(OH)4 from transforming into more mobile forms, while adding these materials to Pb promotes Pb3(PO4)2 formation.

Novel Metallic Crystalline Phase of Li2S3

Poor electrical conductivity of the redox end solid products is one of the most important reasons impeding commercialization of Li–S battery. One of the solid intermediate products, Li2S2, is well-characterized, but the nature of the higher-order polysulfides is still somewhat unknown. In this paper, we focus on Li2S3, investigating its structural and electronic properties. The calculated results based on density functional theory find the cubic phase to be the ground state of Li2S3. Analysis of the vibrational spectrum suggests the cubic Li2S3 to be dynamically stable. The calculated density of states predicts the cubic Li2S3 to be metallic, which is due to excess S2 dimers relative to Li atoms in the unit cell. Moreover, a signature peak at 2471 eV observed in the X-ray absorption near-edge structure spectrum of Li polysulfides has been identified. Overall, the calculated results provide insight into the nature of one of the intermediate Li–S redox solid products, thereby facilitating efforts via a controlled synthesis of conducting Li–S redox species to advance the design of the cathode material for Li–S battery.

Efficient Electrochemical Reduction of CO2 by Ni–N Catalysts with Tunable Performance

Developing highly selective and durable catalysts for electrochemical CO2 reduction (ECR) to valuable chemicals is essential for curbing CO2 emissions into the atmosphere and to close the anthropogenic carbon cycle. Herein, we report facile and scalable synthesis of Ni/NC as an efficient low-cost catalyst for ECR to CO. The electrocatalytic properties of the catalysts can be readily tailored by tuning N configurations and the fraction of single Ni sites in Ni/NC via manipulation of the N precursor and annealing conditions. The Ni/NC catalyst designed by thermal treatment of a composite mixture of carbon black, Ni(II) acetate, and polyacrylonitrile achieved low overpotential CO2 to CO conversion with a Faradaic efficiency (FE) as high as 96.5% at −0.9 V (vs reversible hydrogen electrode, RHE), a current density reaching −12.6 mA cm–2 at −1.2 V (vs RHE) corresponding to a CO turnover frequency of up to 4760 h–1. In addition, high FEs for CO formation (≥84.7%) were obtained in a wide potential range from −0.8 to −1.2 V (vs RHE) on the Ni/NC electrode. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectra in combination with multiple electrochemical results suggested that the pyrrolic N and Ni–N structures concertedly play a determinant role in the catalytic performance of Ni/NC during the CO2 reduction reaction.

Revisiting the Phase Transition of Magnetite under Pressure

Using a highly stoichiometric magnetite, the pressure-induced phase transitions of Fe3O4 have been revisited here by performing Fe K-edge X-ray absorption and magnetic circular dichroism measurements up to P = 65 GPa at room temperature and 71 GPa at 20 K. We have observed a structural transition at around 27 GPa from magnetite to a high-pressure phase h-Fe3O4 with the loss of the net ordered magnetic moments for both temperatures. The orthorhombic CaTi2O4-type (Bbmm) structure of the high-pressure phase h-Fe3O4 has been determined by combining experimental studies and theoretical simulations of the Fe K-edge X-ray absorption near-edge structure spectra. The long-time discussed pressure induced spin crossover, and inverse to normal spinel structure transitions in Fe3O4 can be deterministically excluded from the present study up to ∼65 GPa.

Stable Bimetal-MOF Ultrathin Nanosheets for Pseudocapacitors with Enhanced Performance.

Exploring high-performance metal-organic frameworks (MOFs) for pseudocapacitors is quite meaningful for energy storage. Herein a bimetal NiCo-MOF with ultrathin thickness was prepared via a simple hydrothermal method, which shows excellent electrochemical performance with specific capacitances of 1945.83 and 1700.40 F/g at current densities of 0.5 and 1 A/g, respectively, while maintaining good stability. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy spectra unravel that the strong coupling between Ni and Co species enhances the valence state of Ni2+ in the ultrathin nanosheets, which facilitates the charge transfer during the electrochemical reaction and results in greatly improved pseudocapacitive reactivity. This work provides guidance on the promising prospect of MOF materials for pseudocapacitor applications.

Chemisorption of Anionic Species from the Electrolyte Alters the Surface Electronic Structure and Composition of Photocharged BiVO4

Photocharging has recently been demonstrated as a powerful method to improve the photoelectrochemical water splitting performance of different metal oxide photoanodes, including BiVO4. In this work, we use ambient-pressure X-ray Raman scattering (XRS) spectroscopy to study the surface electronic structure of photocharged BiVO4. The O K edge spectrum was simulated using the finite difference method near-edge structure program package, which revealed a change in electron confinement and occupancy in the conduction band. These insights, combined with ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy analyses, reveal that a surface layer formed during photocharging creates a heterojunction with BiVO4, leading to favorable band bending and strongly reduced surface recombination. The XRS images presented in this work exhibit good agreement with soft X-ray absorption near-edge structure spectra from the literature, demonstrating that XRS is a powerful tool to study the electronic and structural properties of light elements in semiconductors. Our findings provide direct evidence of the electronic modification of a metal oxide photoanode surface as a result of the adsorption of electrolyte anionic species under operating conditions. This work highlights that the surface adsorption of these electrolyte anionic species is likely present in most studies on metal oxide photoanodes and has serious implications for the photoelectrochemical performance analysis and fundamental understanding of these materials.

Understanding the superior sodium-ion storage in a novel Na3.5Mn0.5V1.5(PO4)3 cathode

Na3V2(PO4)3 is one of the most promising cathodes for sodium-ion batteries (SIBs) due to its three-dimensional framework. To meet practical feasibility, the substitution of vanadium with low-cost active elements is urgent. Here the Na+ superionic conductor (NASICON)-type Na3.5Mn0.5V1.5(PO4)3 nanoparticles homogeneously embedded in porous carbon matrix are prepared and investigated as a novel cathode for SIBs. The as-prepared Na3.5Mn0.5V1.5(PO4)3/C could deliver a desirable average discharge potential of 3.43 V vs. Na+/Na with fascinating rate capability of 92.7 mA h g−1 at 60C and impressive capacity retention of 87.2% after 4000 cycles at 20C. In situ X-ray diffraction reveals that the electrochemical process undergoes highly reversible biphasic transition and single phase change with a relatively small volume change (8.21%), ensuring the high structural stability and excellent cyclic capability. The reversible evolution of Mn2+/3+ and V3+/4+ redox couples upon Na+ extraction/insertion has been revealed by the confirmation of valence state via both ex situ X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. The superior performance of Na3.5Mn0.5V1.5(PO4)3 could be attributed to the high electronic/ionic conductivity and low sodium-ion diffusion energy barrier, which is supported by the electrochemical impedance spectroscopy and cyclic voltammetry measurements, as well as density functional theory computations.

Temperature-induced molecule assembly effects on the near-edge X-ray absorption fine-structure spectra of Zn-phthalocyanine layers on Si substrates.

The molecular arrangement of vacuum thermally deposited polycrystalline Zn-phthalocyanine (ZnPc) layers on Si substrates is investigated using near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy in the proximity of the carbon edge at E0 = 287.33 eV. The data were collected as a function of the deposition substrate temperature TS (30, 90, 150°C) and the incidence angle θ (20°, 45°, 70°, 90°) of the synchrotron beam with respect to the sample plane. Each spectrum was analysed by mathematical simulation applying an error function for the carbon edge and a set of Voigt and (asymmetric) Gaussian functions for C1s → π* and C1s → σ* transitions of ZnPc, respectively. It turned out that part of the organic layer consists of adventitious carbon, which does not contribute to the molecular transitions of ZnPc, whereas all molecular features exhibit polarization-dependent peak areas pointing to a reasonable fraction of well-assembled molecules at any TS. The highest adventitious carbon fraction was found at TS = 30°C, whereas the highest polarization dependence was found at TS = 90°C. The calculated average molecular tilt angles for the three temperatures (30, 90, 150°C) were γ = 60.6°, 68.7° and 66.7°, respectively. If only the polarization-dependent fractions are considered, then the three samples can be mathematically described using a shared molecular tilt angle of γ= 68.7°, which corresponds to the average tilt angle of the TS = 90°C sample.

Comparison of local crystal structure and magnetic properties of cation substituted LiNiO2 compositions

We investigate the change in local crystal structure and its impact on the magnetic ground states of LiNi0.5X0.5O2 (X = Mn, Co) and LiNi0.75Y0.25O2 (Y = Fe, Al) and contrast it against LiNiO2. The solid-state synthesis route adopted here introduces some anti-site disorder in the final compositions due to the volatile nature of Li ions. Powder X-ray diffraction (XRD) profiles were hence recorded using a rotating anode X-ray source to determine the percentage of anti-site disorder, and phase purity of all the compositions. Rietveld refinement of the XRD profiles confirms the symmetry and provides the estimation of unit cell parameters. Near-edge X-ray absorption spectra verified the oxidation state of various cations present in the compositions. Analysis of the extended X-ray absorption fine structure spectra identify the signatures of Jahn–Teller distortion in Ni3+ rich compositions. Changes in NiO6 octahedral environment has a much deeper impact on the magnetism of these compositions.

Identifying the local defect structure in (Na0.5K0.5)NbO3: 1 mol. % CuO lead-free ceramics by x-ray absorption spectra

The local defect structure around dopant atoms in 1 mol. % CuO doped (Na0.5K0.5)NbO3 lead-free ceramics was investigated by means of x-ray absorption spectra as compared with the local structure around the host Nb site. The Cu K-edge and O K-edge x-ray absorption near-edge structure spectra demonstrate divalent Cu ions that occupy the octahedrally coordinated Nb sites and also reveal the existence of oxygen vacancy VO¨ in the nearest neighboring around the Cu atom evidently. Moreover, the Cu and Nb K-edge extended x-ray absorption fine structure clearly suggests that the oxygen vacancies should be located at two O22 sites with the two longest Cu-O22 bond lengths, thus producing trimeric bent VO¨-CuNb″′-VO¨ defect complexes with a dipole moment PD parallel to the spontaneous polarization Ps, instead of dimeric CuNb″′-VO¨ and straight VO¨-CuNb″′-VO¨ defect complexes. This kind of special defect structure is also different from that observed in conventional Pb-based perovskite ferroelectrics in which only dimeric CuTi″-VO¨ defect dipoles were observed. Finally, the influence of the defect complexes on the macroscopic properties was specially discussed by taking into account the interaction between Ps and PD.

Polarization dependent X-ray absorption near-edge spectra of boron nitride nanotubes

We report polarization dependent, scanning transmission X-ray microscopy measurements of individual boron nitride nanotubes (BNNTs) and analyze them by means of first-principles calculations. X-ray absorption near-edge spectra of hexagonal boron-nitride (hBN) are calculated as a function of light polarization and layer stacking and best agreement with recent experimental data is obtained for the commonly assumed AA' stacking. Our experimental BNNT spectra show a pronounced polarization dependence which is qualitatively well reproduced in the calculations. We show that the BNNT has a mixed stacking sequence which may explain some of the differences seen between the hBN and BNNT line shapes.

Properties of NTCDA Thin Films on Ag(110): Scanning Tunneling Microscopy, Photoemission, Near-Edge X-ray Fine Structure, and Density Functional Theory Investigations

It is well proven that the properties of organic/metal interfaces play an utmost role in the performance of organic devices. Here we present a study on structural and electronic properties of high-quality 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) films grown on an Ag(110) surface. High-resolution scanning tunneling microscopy and low-energy electron diffraction show the presence of two molecular domains. Density functional theory calculations indicate that the most stable location of NTCDA corresponds to anhydride oxygen attached to the Ag atoms along the [110] direction. Photoemission results of the C 1s and O 1s core levels demonstrate a strong interfacial bonding, inducing a charge transfer from the Ag metal to the molecular monolayer. An angular-dependent study of the C K-edge near-edge X-ray fine structure spectra provides detailed information concerning the evolution of the NTCDA orientation with the film thickness.

Insight into the low-temperature decomposition of Aroclor 1254 over activated carbon-supported bimetallic catalysts obtained with XANES and DFT calculations.

Novel bimetallic catalysts supported on activated carbon (AC) with high metal loadings were synthesized by carbonizing an ion-exchange resin. AC-supported Ni-Cu (Ni-Cu/C) and Ni-Zn (Ni-Zn/C) bimetallic catalysts with different Ni:Cu(Zn) ratios were used to decompose Aroclor 1254, which is a commonly used commercial mixture of polychlorinated biphenyls. Characterization with scanning electron microscopy and energydispersive X-ray spectroscopy showed that the metals were uniformly distributed on the surfaces and inside the catalysts. After 30 min reaction over the Ni-Cu/C catalyst at a low temperature of 250 °C, the efficiencies of Hexa-CBs decomposition present in Aroclor 1254 exceeded 97%, which were higher than those achieved over Ni-Zn/C. These efficiencies increased with Cu content in Ni-Cu/C, and decreased with the amount of Zn in Ni-Zn/C. X-ray photoelectron spectra and X-ray absorption near-edge structure spectra of Ni-Cu/C and Ni-Zn/C before and after the reaction indicated that Ni and Cu were oxidized during the reaction. However, Zn showed no significant change, suggesting that Ni and Cu are the active components to promote reaction with Aroclor 1254, whereas Zn is only a spectator. The efficiencies of Aroclor 1254 decomposition over bimetallic catalysts were greater than those over monometallic catalysts, which was confirmed by density functional theory calculations.

The role of chemical disorder and structural freedom in radiation-induced amorphization of silicon carbide deduced from electron spectroscopy and ab initio simulations

Chemical disorder has previously been proposed as an explanation for the anomalously facile amorphization of silicon carbide (SiC), on the basis of topological connectivity arguments alone. In this exploratory study, “amorphous” (formally, aperiodic) SiC structures produced in ab initio molecular dynamics simulations were assessed for their connectivity topology and used to compute synthetic electron energy-loss spectra (EELS) using the ab initio real-space multiple scattering code FEFF. The synthesized spectra were compared to experimental EELS spectra collected from an ion-amorphized SiC specimen. A threshold level of chemical disorder χ (expressed as the ratio of the number of carbon-carbon bonds to the number of carbon-silicon bonds) was found to be χ ≈ 0.38, above which structural relaxation resulted in formally aperiodic structures. Different disordering methodologies resulted in identifiably different aperiodic structures, as assessed by local-cluster analysis and confirmed by collecting near-edge electron energy-loss spectra (ELNES). Such structural differences are predicted to arise for SiC crystals amorphized by irradiations involving different damage mechanisms—and therefore differing disordering mechanisms—for example, when contrasting the respective amorphized products of ion irradiation, neutron irradiation, and high-energy electron irradiation. Evidence for sp2-hybridized carbon bonding is observed, both experimentally in the irradiated sample and in simulations, and related to connectivity topology-based models for the amorphization of silicon carbide. New information about the probable intermediate-range structures present in amorphized silicon carbide is deduced from enumeration of primitive rings and evolution of local cluster configurations during the ab initio-modelled amorphization sequences.