Absolute oscillator strengths from<i>K</i>-shell electron-energy-loss spectra of the fluoroethenes and 1,3-perfluorobutadiene

McLaren, R.; Clark, S. A.; Ishii, I.; Hitchcock, Adam P.

doi:10.1103/physreva.36.1683

Cited by 155 publications

(105 citation statements)

References 48 publications

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“…Carbon K-edge spectra of 1,1-difluoroethene obtained by TTDFT and CCSD calculations and compared to experiment. Theoretical 1s → π * have been align to experiment, 129 with shift reported beneath each model label as expressed in eV. Basis set aug-cc-pCVDZ for carbon, cc-pVDZ for the remaining elements, and additional Rydberg (3s3p3d) have been centered at the center of the C-C bond.…”

Section: Treating Larger Systemsmentioning

confidence: 99%

“…4.5 the carbon K-edge X-ray absorption spectrum is investigated using the hierarchy of coupled cluster methods CCS, CC2, CCSD, and CCSDR(3), as compared against experiment. 129 Since the CCSDR(3) method only corrects the CCSD energetics and leaves the transition energies unaffected, the results are included as the CCSDR(3) shifts in the panel for CCSD. The integrated absorption cross-sections I S are also reported, in order to investigate the non-variational nature of coupled cluster.…”

Section: Relaxation In the Coupled Cluster Hierarchymentioning

confidence: 99%

“…4.6 the X-ray absorption spectrum of 1,1-difluoroethene is reported, as obtained using TDDFT and CCSD and compared against experiment. 129 For TDDFT a Coulomb-attenuated B3LYP functional with parameters tailored as from Ref. [194] was used, designated CAM-B3LYP 100% , 190 for which good results have been found against experiment.…”

Section: Treating Larger Systemsmentioning

confidence: 99%

“…X-ray absorption spectra of ethene as obtained with a hierarchy of CPP-CC methods and compared against experiment. 129 The results are aligned against the first experimental transition, with corresponding shifts given beneath each model label, as expressed in eV. Included is also the total integrated absorption cross-section IS.…”

mentioning

confidence: 99%

“…Electronic structure theory 129 Basis set designation indicates set for carbon, while hydrogen is given the basic basis set at the corresponding level (i.e. cc-pVDZ or cc-pVTZ).…”

mentioning

confidence: 99%

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X-ray spectroscopies through damped linear response theory

Fransson¹

2016

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In order to reach a fundamental understanding of interactions between electromagnetic radiation and molecular materials, experimental measurements need to be supplemented with theoretical models and simulations. With the use of this combination, it is possible to characterize materials in terms of, e.g., chemical composition and molecular structure, as well as achieve time-resolution in studies of chemical reactions. This doctoral thesis focuses on the development and evaluation of theoretical methods with which, amongst others, X-ray absorption and X-ray emission spectroscopies can be interpreted and predicted. In X-ray absorption spectroscopy the photon energy is tuned such that core electrons are targeted and excited to either bound or continuum states, and X-ray emission spectroscopy measures the subsequent decay from such an excited state. These core excitations/de-excitations exhibit strong relaxation effects, making theoretical considerations of the processes particularly challenging. While the removal of a valence electron leaves the remaining electrons relatively unaffected, removing core electrons has a substantial effect on the other electrons due to the significant change in the screening of the nucleus. Additionally, the core-excited states are embedded in a manifold of valence-excited states that needs to be considered by some computationally feasible method. In this thesis, a damped formalism of linear response theory, which is a perturbative manner of considering the interactions of (weak) external or internal fields with molecular systems, has been utilized to investigate mainly the X-ray absorption spectra of small-to medium-sized molecular systems.Amongst the standard quantum chemical methods available, coupled cluster is perhaps the most accurate, with a well-defined, hierarchical manner of approaching the correct electronic wave function. Combined with response theory, it provides a reliable theoretical method in which relaxation effects are addressed by means of an accurate treatment of electron correlation. The first part of this thesis deals with the development and evaluation of such an approach, and it is shown that the relaxation effects can be addressed by the inclusion of double excitations in the coupled cluster manifold. However, these calculations are computationally very demanding, and in order to treat larger systems the performance of the coupled cluster approach has been compared to that of the less demanding method of timedensity dependent functional theory (TDDFT). Both methods have been used to v vi investigate the X-ray absorption spectrum of water, which has been extensively debated in the scientific community following a relatively recent hypothesis concerning the underlying structure of liquid water. Water exhibits a great number of anomalous properties that stand out from those of most compounds, and the importance of reaching a fundamental understanding of this substance cannot be overstated. It has been demonstrated that TDDFT yields excellent results for liq...

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Section: Treating Larger Systemsmentioning

confidence: 99%

Section: Relaxation In the Coupled Cluster Hierarchymentioning

confidence: 99%

Section: Treating Larger Systemsmentioning

confidence: 99%

mentioning

confidence: 99%

“…Electronic structure theory 129 Basis set designation indicates set for carbon, while hydrogen is given the basic basis set at the corresponding level (i.e. cc-pVDZ or cc-pVTZ).…”

mentioning

confidence: 99%

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X-ray spectroscopies through damped linear response theory

Fransson¹

2016

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Annealing and ultraviolet treatment of plasma fluorocarbon films for enhanced cohesion and stability

Chevallier¹,

Holvoet²,

Turgeon³

et al. 2010

J of Applied Polymer Sci

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Stents, commonly used for the treatment of cardiovascular diseases, are mainly made of 316L stainless steel. They are, however, prone to corrosion when they are in contact with human body fluid. To prevent this corrosion process and to ameliorate their patencies, in this study, we used a strategy to cover stent materials with a protective fluorocarbon layer deposited by plasma polymerization. In an approach to optimize its cohesion properties and stability, posttreatments, namely, thermal annealing and UV irradiation, were applied on the ultrathin fluorocarbon film. A combination of X-ray photoelectron spectroscopy, polarized near-edge X-ray absorption fine-structure spectroscopy, and time-of-flight secondary ion mass spectrometry demonstrated that UV treatment led to chain scission and film crosslinking and, in this way, decreased the amount and/or size of nanoscaled defects originally present in the films. Annealing on the other hand induced a film reorganization in favor of longer, well-ordered fluorocarbon chains. However, a deformation process that was applied to study the film adhesion properties induced chain scissions with reorganization. Aging tests exhibited an oxidation of the topmost layer for both the as-deposited and posttreated samples. Finally, the film stability was improved after UV treatment for both the nondeformed and deformed samples.

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Band‐gap Modification in a Nanoscale Region of Polyethylene by Fast Electrons

Kim

2009

ChemPhysChem

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Drastic change: A nanoscale spot of polyethylene (PE) can change its electrical properties dramatically after exposure to fast electrons-from a representative insulator, via a semiconductor, to a hopping conductor (see picture). These modifications of the chemical and energy-band structures of PE are extremely localized, thus opening a new way to use this conventional polymer in nanotechnology. Herein, a nanoscale area on a polyethylene film is investigated by an electron-microscope-electron-spectroscopy system after exposure to various doses of fast electrons. Therefore, modifications in its physical and chemical properties and the spatial size of a beam-affected area are measured. The results show that the modifications of PE by electrons are significant enough to rebuild the chemical and energy-band structures. Hydrogen is removed through scission while pi bonds are formed by cross-linking between main chains. These changes cause the energy band of PE to show dramatic variation from a wide to a narrow (down to approximately 0.8 eV) band-gap. At the highest dose (10(10) C m(-2)) used herein, an illuminated area of PE becomes quite similar in properties to graphitic amorphous carbon. On the other hand, the size of the beam-affected area is as small as roughly 50 nm in diameter. Since the extent of the modifications can be tailored in a controllable way by the dose, these findings may be fundamental for the utilization of a conventional polymer in nanotechnology.

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Absolute oscillator strengths fromK-shell electron-energy-loss spectra of the fluoroethenes and 1,3-perfluorobutadiene

Cited by 155 publications

References 48 publications

X-ray spectroscopies through damped linear response theory

X-ray spectroscopies through damped linear response theory

Annealing and ultraviolet treatment of plasma fluorocarbon films for enhanced cohesion and stability

Band‐gap Modification in a Nanoscale Region of Polyethylene by Fast Electrons

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