Bloch theorem for crystals with structural distortions

CO2 Activation on Heterostructures of Bi2O3-Nanocluster Modified TiO2: Promoting the Critical First Step in CO2 Conversion

10.26434/chemrxiv.5917351.v1 ◽

2018 ◽

Cited By ~ 1

Author(s):

Michael Nolan

Keyword(s):

Metal Oxide ◽

Density Functional ◽

Initial Step ◽

Difficult Problem ◽

Carbonate Formation ◽

Structural Distortions ◽

Strong Adsorption ◽

Two Factors ◽

Key Steps ◽

Recent Experimental Work

The conversion of CO2 to fuels is of significant importance in enabling the production of sustainable fuels, contributing to alleviating greenhouse gas emissions. While there are a number of key steps required to convert CO2, the initial step of adsorption and activation by the catalyst is critical. Well-known metal oxides such as oxidised TiO2 or CeO2 are unable to promote this step. In addressing this difficult problem, recent experimental work shows the potential for bismuth-containing materials to activate and convert CO2, but the origin of this activity is not yet clear. Additionally, nanostructures can show enhanced activity towards CO2. In this paper we present density functional theory (DFT) simulations of CO2 activation on heterostructured materials composed of extended rutile and anatase TiO2 surfaces modified with nanoclusters with Bi2O3 stoichiometry. These heterostructures show low coordinated Bi sites in the nanoclusters and a valence band edge that is dominated by Bi-O states. These two factors mean that supported Bi2O3 nanoclusters are able to adsorb and activate CO2. Computed adsorption energies lie in the range of -0.54 eV to -1.01 eV. In these strong adsorption modes, CO2 is activated, in which the molecule bends giving O-C-O angles of 126 - 130o and elongation of C-O distances up to 1.28 Å, with no carbonate formation. The electronic properties show a strong CO2-Bi-oxygen interaction that drives the interaction of CO2 to induce the structural distortions. Bi2O3-TiO2 heterostructures can be reduced to form Bi2+ and Ti3+ species. The interaction of CO2 with this electron-rich, reduced system can produce CO directly, reoxidising the heterostructure or form an activated carboxyl species (CO2-) through electron transfer from the heterostructure to CO2. These results highlight that a semiconducting metal oxide modified with suitable metal oxide nanoclusters can activate CO2, thus overcoming the difficulties associated with the difficult first step in CO2 conversion.

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To Bend or Not to Bend, the Dilemma of Multiple Bonds

10.26434/chemrxiv.8066747.v1 ◽

2019 ◽

Author(s):

Michele Pizzocchero ◽

Matteo Bonfanti ◽

Rocco Martinazzo

Keyword(s):

First Principles ◽

2D Materials ◽

Main Group ◽

First Principles Calculations ◽

Group 14 ◽

Multiple Bonds ◽

Main Group Elements ◽

Structural Distortions

The manuscript addresses the issue of the structural distortions occurring at multiple bonds between high main group elements, focusing on group 14. These distortions are known as trans-bending in silenes, disilenes and higher group analogues, and buckling in 2D materials likes silicene and germanene. A simple but correlated \sigma + \pi model is developed and validated with first-principles calculations, and used to explain the different behaviour of second- and higher- row elements.

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Photoinduced Self-Localized Structural Distortions in YBa2Cu3O7-delta: Direct Evidence of Polarons or Bipolarons

10.21236/ada196091 ◽

1988 ◽

Author(s):

Y. H. Kim ◽

C. F. Foster ◽

A. J. Heeger ◽

S. Cox ◽

G. Stucky

Keyword(s):

Direct Evidence ◽

Structural Distortions

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Quality Assessment of 3D Synthesized Images Based on Textural and Structural Distortion Estimation

Applied Sciences ◽

10.3390/app11062666 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2666

Author(s):

Hafiz Muhammad Usama Hassan Alvi ◽

Muhammad Shahid Farid ◽

Muhammad Hassan Khan ◽

Marcin Grzegorzek

Keyword(s):

Quality Assessment ◽

Mixed Reality ◽

Depth Estimation ◽

Poor Quality ◽

Depth Image ◽

Depth Maps ◽

Structural Distortions ◽

Image Quality Metric ◽

Technological Constraints

Emerging 3D-related technologies such as augmented reality, virtual reality, mixed reality, and stereoscopy have gained remarkable growth due to their numerous applications in the entertainment, gaming, and electromedical industries. In particular, the 3D television (3DTV) and free-viewpoint television (FTV) enhance viewers’ television experience by providing immersion. They need an infinite number of views to provide a full parallax to the viewer, which is not practical due to various financial and technological constraints. Therefore, novel 3D views are generated from a set of available views and their depth maps using depth-image-based rendering (DIBR) techniques. The quality of a DIBR-synthesized image may be compromised for several reasons, e.g., inaccurate depth estimation. Since depth is important in this application, inaccuracies in depth maps lead to different textural and structural distortions that degrade the quality of the generated image and result in a poor quality of experience (QoE). Therefore, quality assessment DIBR-generated images are essential to guarantee an appreciative QoE. This paper aims at estimating the quality of DIBR-synthesized images and proposes a novel 3D objective image quality metric. The proposed algorithm aims to measure both textural and structural distortions in the DIBR image by exploiting the contrast sensitivity and the Hausdorff distance, respectively. The two measures are combined to estimate an overall quality score. The experimental evaluations performed on the benchmark MCL-3D dataset show that the proposed metric is reliable and accurate, and performs better than existing 2D and 3D quality assessment metrics.

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Dynamic lattice distortions driven by surface trapping in semiconductor nanocrystals

Nature Communications ◽

10.1038/s41467-021-22116-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Burak Guzelturk ◽

Benjamin L. Cotts ◽

Dipti Jasrasaria ◽

John P. Philbin ◽

David A. Hanifi ◽

...

Keyword(s):

Photon Energy ◽

Semiconductor Nanocrystals ◽

Atomic Scale ◽

Atomistic Simulations ◽

Shell System ◽

Structural Distortions ◽

Colloidal Semiconductor Nanocrystals ◽

Femtosecond Electron Diffraction ◽

Structural Deformations ◽

Nonradiative Processes

AbstractNonradiative processes limit optoelectronic functionality of nanocrystals and curb their device performance. Nevertheless, the dynamic structural origins of nonradiative relaxations in such materials are not understood. Here, femtosecond electron diffraction measurements corroborated by atomistic simulations uncover transient lattice deformations accompanying radiationless electronic processes in colloidal semiconductor nanocrystals. Investigation of the excitation energy dependence in a core/shell system shows that hot carriers created by a photon energy considerably larger than the bandgap induce structural distortions at nanocrystal surfaces on few picosecond timescales associated with the localization of trapped holes. On the other hand, carriers created by a photon energy close to the bandgap of the core in the same system result in transient lattice heating that occurs on a much longer 200 picosecond timescale, dominated by an Auger heating mechanism. Elucidation of the structural deformations associated with the surface trapping of hot holes provides atomic-scale insights into the mechanisms deteriorating optoelectronic performance and a pathway towards minimizing these losses in nanocrystal devices.

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Does False Consciousness Necessarily Preclude Moral Blameworthiness?: The Refusal of the Women Antisuffragists

Hypatia ◽

10.1017/hyp.2021.27 ◽

2021 ◽

pp. 1-22

Author(s):

Lee Wilson

Keyword(s):

Recent Work ◽

Epistemic Injustice ◽

Victim Blaming ◽

False Consciousness ◽

Group Level ◽

Moral Agents ◽

Knowledge Practices ◽

Structural Distortions ◽

In Virtue Of

Abstract Social philosophers often invoke the concept of false consciousness in their analyses, referring to a set of evidence-resistant, ignorant attitudes held by otherwise sound epistemic agents, systematically occurring in virtue of, and motivating them to perpetuate, structural oppression. But there is a worry that appealing to the notion in questions of responsibility for the harm suffered by members of oppressed groups is victim-blaming. Individuals under false consciousness allegedly systematically fail the relevant rationality and epistemic conditions due to structural distortions of reasoning or knowledge practices, undermining their status as responsible moral agents. But attending to the constitutive mechanisms and heterogeneity of false consciousness enables us to see how having it does not in itself render someone an inappropriate target of blame. I focus here on the 1889 antisuffragist manifesto “An Appeal against Female Suffrage,” arguing that its signatories, despite false consciousness, satisfy both conditions for ordinary blameworthiness. I consider three prominent signatories, observing that the irrationality characterization is unsustainable beyond group-level diagnoses, and that their capacity to respond appropriately to reasons was not compromised. Following recent work on epistemic injustice, I also argue that culpable mechanisms constituted their false consciousness, rendering them blameworthy for the Appeal.

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Relating diffraction and spectral data of aperiodic tilings: Towards a Bloch theorem

Journal of Geometry and Physics ◽

10.1016/j.geomphys.2021.104217 ◽

2021 ◽

pp. 104217

Author(s):

Eric Akkermans ◽

Yaroslav Don ◽

Jonathan Rosenberg ◽

Claude L. Schochet

Keyword(s):

Spectral Data ◽

Aperiodic Tilings ◽

Bloch Theorem

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Deciphering the influence of structural distortions on the uniaxial magnetic anisotropy of pentagonal bipyramidal Ni(ii) complexes

Chemical Communications ◽

10.1039/c9cc05032a ◽

2019 ◽

Vol 55 (77) ◽

pp. 11547-11550

Author(s):

Mamon Dey ◽

Prashurya Pritam Mudoi ◽

Anup Choudhury ◽

Bipul Sarma ◽

Nayanmoni Gogoi

Keyword(s):

Magnetic Anisotropy ◽

Structural Distortion ◽

Uniaxial Magnetic Anisotropy ◽

Simple Strategy ◽

Structural Distortions

Role of structural distortion on the uniaxial magnetic anisotropy of pentagonal bipyramidal Ni(ii) complexes is explored. A simple strategy to enhance the uniaxial magnetic anisotropy in pentagonal bipyramidal Ni(ii) complexes is proposed.

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