Atomistic Simulations of Vibrational Modes of Crystalline Nanoinclusions in an Amorphous Matrix

2017 ◽  
pp. 207-236
Author(s):  
Tanguy Damart ◽  
Yaroslav M. Beltukov ◽  
Amani Tlili ◽  
Anne Tanguy
1992 ◽  
Vol 283 ◽  
Author(s):  
R. E. Hummel ◽  
S.-S. Chang ◽  
M. Ludwig ◽  
A. Morrone

ABSTRACTPorous silicon which has been prepared by a “dry” technique, that is, by spark erosion, yields similar photoluminescence spectra as anodically etched porous silicon which has been prepared in aqueous solutions. Fourier transform infrared spectra reveal that the dominant features in spark eroded silicon are the Si-O-Si stretching mode and the Si-O-Si bending mode. No infrared vibrational modes characteristic for siloxene have been found in spark eroded Si. Results from X-ray and electron diffraction studies suggest that spark eroded Si involves minute polycrystalline silicon particles which are imbedded in an amorphous matrix.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nidhi Pandey ◽  
Debasattam Pal ◽  
Dipankar Saha ◽  
Swaroop Ganguly

AbstractOlfaction is not as well-understood as vision or audition, nor technologically addressed. Here, Chemical Graph Theory is shown to connect the vibrational spectrum of an odorant molecule, invoked in the Vibration Theory of Olfaction, to its structure, which is germane to the orthodox Shape Theory. Atomistic simulations yield the Eigen-VAlue (EVA) vibrational pseudo-spectra for 20 odorant molecules grouped into 6 different ‘perceptual’ classes by odour. The EVA is decomposed into peaks corresponding to different types of vibrational modes. A novel secondary pseudo-spectrum, informed by this physical insight—the Peak-Decomposed EVA (PD-EVA)—has been proposed here. Unsupervised Machine Learning (spectral clustering), applied to the PD-EVA, clusters the odours into different ‘physical’ (vibrational) classes that match the ‘perceptual’, and also reveal inherent perceptual subclasses. This establishes a physical basis for vibration-based odour classification, harmonizes the Shape and Vibration theories, and points to vibration-based sensing as a promising path towards a biomimetic electronic nose.


2015 ◽  
Vol 17 (6) ◽  
pp. 4625-4633 ◽  
Author(s):  
Anurag Prakash Sunda ◽  
Anirban Mondal ◽  
Sundaram Balasubramanian

Structural correlations and signature of cation–anion hydrogen bonding in ammonium triflate protic ionic liquids at varying length of the alkyl tail.


2020 ◽  
Author(s):  
Steven Huss ◽  
Sikai Wu ◽  
Bo Chen ◽  
Tao Wang ◽  
Margaret Gerthoffer ◽  
...  

<div><div><div><p>Carbon nanothreads, which are unique one-dimensional sp3-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids are constructed through pressure-induced polymerization of sp2 molecules such as benzene. Whereas a few examples of carbon nanothreads have been reported, the need for high onset pressures ( ≥ 17 GPa) to synthesize them precludes scalability and limits scope. Herein, we report the scalable synthesis of carbon nanothreads based on molecular furan, which can be achieved through ambient temperature pressure-induced polymerization with an onset reaction pressure of only 10 GPa due to its lessened aromaticity relative to other molecular precursors. When slowly compressed to 15 GPa and gradually decompressed to 1.5 GPa, a sharp six-fold diffraction pattern is observed in situ, indicating a well‐ordered crystalline material formed from liquid furan. Single-crystal X-ray diffraction of the reaction product exhibits three distinct d-spacings from 4.75 to 4.9 Å, whose size, angular spacing, and degree of anisotropy are consistent with our atomistic simulations for crystals of furan nanothreads. Further evidence for polymerization was obtained by powder XRD and Raman/IR spectroscopy. Comparison of the IR spectra with computed vibrational modes provides identification of spectral features characteristic of specific nanothreads, namely syn, anti, and syn/anti configurations. Furan therefore presents a strategic entry toward scalable carbon nanothreads.</p></div></div></div>


2020 ◽  
Author(s):  
Steven Huss ◽  
Sikai Wu ◽  
Bo Chen ◽  
Tao Wang ◽  
Margaret Gerthoffer ◽  
...  

<div><div><div><p>Carbon nanothreads, which are unique one-dimensional sp3-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids are constructed through pressure-induced polymerization of sp2 molecules such as benzene. Whereas a few examples of carbon nanothreads have been reported, the need for high onset pressures ( ≥ 17 GPa) to synthesize them precludes scalability and limits scope. Herein, we report the scalable synthesis of carbon nanothreads based on molecular furan, which can be achieved through ambient temperature pressure-induced polymerization with an onset reaction pressure of only 10 GPa due to its lessened aromaticity relative to other molecular precursors. When slowly compressed to 15 GPa and gradually decompressed to 1.5 GPa, a sharp six-fold diffraction pattern is observed in situ, indicating a well‐ordered crystalline material formed from liquid furan. Single-crystal X-ray diffraction of the reaction product exhibits three distinct d-spacings from 4.75 to 4.9 Å, whose size, angular spacing, and degree of anisotropy are consistent with our atomistic simulations for crystals of furan nanothreads. Further evidence for polymerization was obtained by powder XRD and Raman/IR spectroscopy. Comparison of the IR spectra with computed vibrational modes provides identification of spectral features characteristic of specific nanothreads, namely syn, anti, and syn/anti configurations. Furan therefore presents a strategic entry toward scalable carbon nanothreads.</p></div></div></div>


Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.


Author(s):  
S. Trachtenberg ◽  
P.M. Steinert ◽  
B.L. Trus ◽  
A.C. Steven

During terminal differentiation of vertebrate epidermis, certain specific keratin intermediate filament (KIF) proteins are produced. Keratinization of the epidermis involves cell death and disruption of the cytoplasm, leaving a network of KIF embedded in an amorphous matrix which forms the outer horny layer known as the stratum corneum. Eventually these cells are shed (desquamation). Normally, the processes of differentiation, keratinization, and desquamation are regulated in an orderly manner. In psoriasis, a chronic skin disease, a hyperkeratotic stratum corneum is produced, resulting in abnormal desquamation of unusually large scales. In this disease, the normal KIF proteins are diminished in amount or absent, and other proteins more typical of proliferative epidermal cells are present. There is also evidence of proteolytic degradation of the KIF.


1992 ◽  
Vol 2 (10) ◽  
pp. 1929-1939 ◽  
Author(s):  
Mariette Barthes ◽  
Juegen Eckert ◽  
Susanna W. Johnson ◽  
Jacques Moret ◽  
Basil I. Swanson ◽  
...  

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