Asymmetric deformation density analysis in carbon nanotubes

2020 ◽  
Vol 120 (17) ◽  
Author(s):  
Samad Amini ◽  
Seyed Mohammad Azami
Keyword(s):  
Carbon Nanotubes ◽  
Asymmetric Deformation ◽  
Deformation Density ◽  
Density Analysis

Electron Deformation Density Distribution in α-Boron

1987 ◽  
Vol 97 ◽  
Author(s):  
G. Will ◽  
B. Kiefer ◽  
B. Morosin ◽  
G. A. Slack
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Distribution Free ◽  
Deformation Density ◽  
Difference Density ◽  
Density Maps ◽  
Density Analysis ◽  
Electron Density Analysis

ABSTRACTThe bonding features of α-boron were studied using electron density analysis procedures. Deformation density maps and valence density were calculated and the structure analysed by so-called multipole refinements, yielding R - 0.0119. The refinement model correctly describes the bonding and results in a difference density distribution free from any meaningful residual peaks.

Three trithiadiazepines and a trithiatriazepine

2013 ◽  
Vol 70 (1) ◽  
pp. 60-66 ◽  
Author(s):  
Ray Jones
Keyword(s):  
Electron Density ◽  
Aromatic Ring ◽  
Intermolecular Interactions ◽  
Experimental Studies ◽  
Asymmetric Unit ◽  
Effect Of Substituents ◽  
Deformation Density ◽  
Density Analysis ◽  
Derivatives Of ◽  
Bonding Electron

The structures of 6-nitro-1,3λ4δ2,5,2,4-trithiadiazepine [C2HN3O2S3, (1)], 6,7-dinitro-1,3λ4δ2,5,2,4-trithiadiazepine [C2N4O4S3, (2)], 1,3λ4δ2,5,2,4-trithiadiazepine-6,7-dicarbonitrile [C4N4S3, (3)] and 7-acetyl-1,3λ4δ2,5,2,4,6-trithiatriazepine [C3H3N3OS3, (4)] presented here include the most precise determinations of these seven-membered 10 π-electron aromatic ring systems published to date. Both (2) and (3) are sited around crystallographic twofold axes with half a molecule per asymmetric unit. Comparison with other published derivatives of these rings reveals the effect of substituents on bonding, conformations and intermolecular interactions, including π-stacking. The deformation density analysis of (2) is consistent with the expected bonding electron density from other theoretical and experimental studies.

scholarly journals How amino and nitro substituents direct electrophilic aromatic substitution in benzene: an explanation with Kohn–Sham molecular orbital theory and Voronoi deformation density analysis

2016 ◽  
Vol 18 (17) ◽  
pp. 11624-11633 ◽  
Author(s):  
O. A. Stasyuk ◽  
H. Szatylowicz ◽  
T. M. Krygowski ◽  
C. Fonseca Guerra
Keyword(s):  
Molecular Orbital ◽  
Electrophilic Substitution ◽  
Molecular Orbitals ◽  
Electrophilic Aromatic Substitution ◽  
Molecular Orbital Theory ◽  
Aromatic Substitution ◽  
Orbital Theory ◽  
Deformation Density ◽  
Density Analysis

Molecular orbitals of aniline explain electrophilic substitution, whereas for nitrobenzene charge rearrangements are needed.

Reducing Variability in Chemical Vapor Deposition of Carbon Nanotubes Based on Gas Purification and Sample Support Redesign

2020 ◽  
Author(s):  
Golnaz Tomaraei ◽  
Moataz Abdulhafez ◽  
Jaegeun Lee ◽  
Mostafa Bedewy
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Gas Flows ◽  
Structure Property ◽  
Fundamental Study ◽  
Forest Height ◽  
Density Analysis ◽  
Vertically Aligned

Abstract The synthesis of vertically aligned carbon nanotubes (CNTs), also referred to as CNT forest, by chemical vapor deposition (CVD) is an intricate process that is sensitive to multiple factors other than control of temperature, pressure, and gas flows. In particular, growth is highly sensitive to factors like ambient humidity, as well as small quantities of oxygen-containing species and carbon deposits inside the reactor. These typically uncontrolled factors significantly affect growth reproducibility and hinders the fundamental study of process-structure-property relationship for these emerging materials. Accordingly, universally applicable design modifications and process steps toward improve growth consistency are sought after. In this study, we introduce two new modifications to our custom-designed multizone rapid thermal CVD reactor and demonstrate their impact on growth: (1) reconfiguring the inlet gas plumbing to add a gas purifier to the helium (He) line, and (2) designing a new support wafer for consistent loading of substrates. We use statistical analysis to test the effectiveness of these modifications in improving growth and reducing variability of both CNT forest height and density. Analysis of our experimental results and hypothesis testing show that combining the implementation of He purifier with the redesigned support wafer increases forest height and reduces the variability in height (17-folds), both at statistically significant and practically significant levels.

Reducing Variability in Chemical Vapor Deposition of Carbon Nanotubes Based On Gas Purification and Sample Support Redesign

2021 ◽  
Author(s):  
Golnaz Tomaraei ◽  
Jaegeun Lee ◽  
Moataz Abdulhafez ◽  
Mostafa Bedewy
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Gas Flows ◽  
Structure Property ◽  
Fundamental Study ◽  
Forest Height ◽  
Density Analysis ◽  
Vertically Aligned

Abstract The synthesis of vertically aligned carbon nanotubes (CNTs), also referred to as CNT forest, by chemical vapor deposition (CVD) is an intricate process that is sensitive to multiple factors other than control of temperature, pressure, and gas flows. In particular, growth is highly sensitive to factors like ambient humidity, as well as small quantities of oxygen-containing species and carbon deposits inside the reactor. These typically uncontrolled factors significantly affect growth reproducibility and hinders the fundamental study of process-structure-property relationship for these emerging materials. Accordingly, universally applicable design modifications and process steps toward improving growth consistency are sought after. In this study, we introduce two new modifications to our custom-designed multizone rapid thermal CVD reactor and demonstrate their impact on growth: (1) reconfiguring the inlet gas plumbing to add a gas purifier to the helium (He) line, and (2) designing a new support wafer for consistent loading of substrates. We use statistical analysis to test the effectiveness of these modifications in improving growth and reducing variability of both CNT forest height and density. Analysis of our experimental results and hypothesis testing show that combining the implementation of He purifier with the redesigned support wafer increases forest height and reduces the variability in height (17-folds), both at statistically significant and practically significant levels.

Structural phenomena in the growth of carbon nanotubes

1993 ◽  
Vol 51 ◽  
pp. 750-751
Author(s):  
Jun Jiao
Keyword(s):  
Carbon Nanotubes ◽  
Growth Mechanism ◽  
Carbonaceous Material ◽  
Cluster Growth ◽  
Structural Elements ◽  
Rich Variety ◽  
Different Shapes ◽  
Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

Sign in / Sign up

Export Citation Format

Share Document