Journal articles: 'Densité de chiralité'

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Ahmed Jamal, G. R., M. Rezanur Islam, M. Adnan Rahman, J. Ferdous Meem, and R. Akter Sathie. "Chirality Dependence of Gas Adsorption Property of Single Wall Carbon Nanotubes." Materials Science Forum 889 (March 2017): 248–52. http://dx.doi.org/10.4028/www.scientific.net/msf.889.248.

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In this work, effect of chirality on gas adsorption property of semiconducting single-wall carbon nanotubes (SWCNTs) is reported for the first time. First principles simulation of the interaction of three different chirality SWCNTs with different gas molecules is performed maintaining equilibrium tube–molecule distance. Results are obtained employing density functional theory, using the Atomistic toolkit simulation package (ATK-DFT). Nanotube density of states is observed to vary significantly due to interaction with different types of gases as well as for same gas if chirality of SWCNTs varies. The most significant finding is, the change in DOS near Fermi level is highest in mod 2 type semiconducting SWCNT for different gas molecules irrespective of donor or acceptor. Thus, proper selection of chirality of SWCNT is important to make nanotube based gas sensor and mod 2 types semiconducting SWCNTs should get preference over mod 1 type as a sensing element so as to get better sensitivity.

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Kharlamova, Marianna V., Maria G. Burdanova, Maksim I. Paukov, and Christian Kramberger. "Synthesis, Sorting, and Applications of Single-Chirality Single-Walled Carbon Nanotubes." Materials 15, no. 17 (August 26, 2022): 5898. http://dx.doi.org/10.3390/ma15175898.

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The synthesis of high-quality chirality-pure single-walled carbon nanotubes (SWCNTs) is vital for their applications. It is of high importance to modernize the synthesis processes to decrease the synthesis temperature and improve the quality and yield of SWCNTs. This review is dedicated to the chirality-selective synthesis, sorting of SWCNTs, and applications of chirality-pure SWCNTs. The review begins with a description of growth mechanisms of carbon nanotubes. Then, we discuss the synthesis methods of semiconducting and metallic conductivity-type and single-chirality SWCNTs, such as the epitaxial growth method of SWCNT (“cloning”) using nanocarbon seeds, the growth method using nanocarbon segments obtained by organic synthesis, and the catalyst-mediated chemical vapor deposition synthesis. Then, we discuss the separation methods of SWCNTs by conductivity type, such as electrophoresis (dielectrophoresis), density gradient ultracentrifugation (DGC), low-speed DGC, ultrahigh DGC, chromatography, two-phase separation, selective solubilization, and selective reaction methods and techniques for single-chirality separation of SWCNTs, including density gradient centrifugation, two-phase separation, and chromatography methods. Finally, the applications of separated SWCNTs, such as field-effect transistors (FETs), sensors, light emitters and photodetectors, transparent electrodes, photovoltaics (solar cells), batteries, bioimaging, and other applications, are presented.

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García-Toral, Dolores, Raúl Mendoza-Báez, Ernesto Chigo-Anota, Antonio Flores-Riveros, Víctor M. Vázquez-Báez, Gregorio Hernández Cocoletzi, and Juan Francisco Rivas-Silva. "Structural Stability and Electronic Properties of Boron Phosphide Nanotubes: A Density Functional Theory Perspective." Symmetry 14, no. 5 (May 9, 2022): 964. http://dx.doi.org/10.3390/sym14050964.

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Based on the Density Functional Theory (DFT) calculations, we analyze the structural and electronic properties of boron phosphide nanotubes (BPNTs) as functions of chirality. The DFT calculations are performed using the M06-2X method in conjunction with the 6-31G(d) divided valence basis set. All nanostructures, (n,0) BPNT (n = 5–8, 10, 12, 14) and (n,n) BPNT (n = 3–11), were optimized minimizing the total energy, assuming a non-magnetic nature and a total charge neutrality. Results show that the BPNT diameter size increases linearly with the chiral index “n” for both chiralities. According to the global molecular descriptors, the (3,3) BPNT is the most stable structure provided that it shows the largest global hardness value. The low chirality (5,0) BPNT has a strong electrophilic character, and it is the most conductive system due to the small |HOMO-LUMO| energy gap. The chemical potential and electrophilicity index in the zigzag-type BPNTs show remarkable chirality-dependent behavior. The increase in diameter/chirality causes a gradual decrease in the |HOMO-LUMO| energy gap for the zigzag BPNTs; however, in the armchair-type BPNTs, a phase transition is generated from a semiconductor to a conductor system. Therefore, the nanostructures investigated in this work may be suggested for both electrical and biophysical applications.

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Fluekiger, P., J. Weber, R. Chiarelli, A. Rassat, and Y. Ellinger. "Chirality and spin density: Ab initio and density functional approaches." International Journal of Quantum Chemistry 45, no. 6 (1993): 649–63. http://dx.doi.org/10.1002/qua.560450614.

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Fecher, Gerhard H., Jürgen Kübler, and Claudia Felser. "Chirality in the Solid State: Chiral Crystal Structures in Chiral and Achiral Space Groups." Materials 15, no. 17 (August 23, 2022): 5812. http://dx.doi.org/10.3390/ma15175812.

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Chirality depends on particular symmetries. For crystal structures it describes the absence of mirror planes and inversion centers, and in addition to translations, only rotations are allowed as symmetry elements. However, chiral space groups have additional restrictions on the allowed screw rotations as a symmetry element, because they always appear in enantiomorphous pairs. This study classifies and distinguishes the chiral structures and space groups. Chirality is quantified using Hausdorff distances and continuous chirality measures and selected crystal structures are reported. Chirality is discussed for bulk solids and their surfaces. Moreover, the band structure, and thus, the density of states, is found to be affected by the same crystal parameters as chirality. However, it is independent of handedness. The Berry curvature, as a topological measure of the electronic structure, depends on the handedness but is not proof of chirality because it responds to the inversion of a structure. For molecules, optical circular dichroism is one of the most important measures for chirality. Thus, it is proposed in this study that the circular dichroism in the angular distribution of photoelectrons in high symmetry configurations can be used to distinguish the handedness of chiral solids and their surfaces.

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Nori-Shargh, Davood, Bita Soltani, Saeed Jameh-Bozorghi, and Mohammad-Reza Talei Bavil Olyai. "Ab initio Study of Configurations of Cycloundeca-1,2,4,5,7,8,10-heptaene." Journal of Chemical Research 2002, no. 11 (November 2002): 544–46. http://dx.doi.org/10.3184/030823402103170943.

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Ab initio molecular orbital and density function theory (DFT) calculations as used to calculate the structure optimisation and configurational features of cycloundeca-1,2,4,5,7,8,10-heptaene (2) showed that the combination of two allenic units of the same chirality and a unit of opposite chirality yields an enantiomeric Z-isomer pair ( RSR and SRS) of C2 symmetry, which is the most stable configuration.

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Cambré, Sofie, Pieter Muyshondt, Remi Federicci, and Wim Wenseleers. "Chirality-dependent densities of carbon nanotubes by in situ 2D fluorescence-excitation and Raman characterisation in a density gradient after ultracentrifugation." Nanoscale 7, no. 47 (2015): 20015–24. http://dx.doi.org/10.1039/c5nr06020f.

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8

van Wezel, Jasper. "Chirality and orbital order in charge density waves." EPL (Europhysics Letters) 96, no. 6 (December 1, 2011): 67011. http://dx.doi.org/10.1209/0295-5075/96/67011.

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9

Morita, Hayato E., Takashi S. Kodama, and Takeyuki Tanaka. "Chirality of camphor derivatives by density functional theory." Chirality 18, no. 10 (2006): 783–89. http://dx.doi.org/10.1002/chir.20302.

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10

Kimmins, Scott D., Saltuk B. Hanay, Robert Murphy, Joanne O’Dwyer, Jessica Ramalho, Emily J. Ryan, Cathal J. Kearney, et al. "Antimicrobial and degradable triazolinedione (TAD) crosslinked polypeptide hydrogels." Journal of Materials Chemistry B 9, no. 27 (2021): 5456–64. http://dx.doi.org/10.1039/d1tb00776a.

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Brunner, Henri, Takashi Tsuno, and Gábor Balázs. "A Chirality Chain in Phenylglycine, Phenylpropionic Acid, and Ibuprofen." Symmetry 13, no. 1 (December 31, 2020): 55. http://dx.doi.org/10.3390/sym13010055.

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Our strategy to analyze the structures of natural amino acids with respect to the interaction of three different elements of chirality within the molecules was applied to the non-natural amino acid (S)-α-phenylglycine, its analogue (S)-α-phenylpropionic acid, and the drug (S)-ibuprofen. The three chirality elements are the configuration at Cα, the conformation at the Cα-C’ bond, and the distortion of the planar carboxylic group to a flat asymmetric tetrahedron. In all three compounds, a given (S) configuration at Cα predominantly induces (M) conformation at the Cα-C’ bond, which in turn preferentially distorts the carboxylic group to a tetrahedron with (R) configuration. Both steps of this chirality chain display high selectivities. Due to varying co-crystallization partners, in all the structures the molecules are in different environments with respect to packing and hydrogen bonding. Nevertheless, the structural pattern and the diaselectivities of the chirality chain persist. For phenylglycine, DFT (Density Functional Theory) calculations confirm the structural results.

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Peng, J., and Q. B. Chen. "Covariant density functional theory for nuclear chirality in 135Nd." Physics Letters B 810 (November 2020): 135795. http://dx.doi.org/10.1016/j.physletb.2020.135795.

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13

Crimin, Frances, Neel Mackinnon, Jörg Götte, and Stephen Barnett. "Optical Helicity and Chirality: Conservation and Sources." Applied Sciences 9, no. 5 (February 26, 2019): 828. http://dx.doi.org/10.3390/app9050828.

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We consider the helicity and chirality of the free electromagnetic field, and advocate the former as a means of characterising the interaction of chiral light with matter. This is in view of the intuitive quantum form of the helicity density operator, and of the dual symmetry transformation generated by its conservation. We go on to review the form of the helicity density and its associated continuity equation in free space, in the presence of local currents and charges, and upon interaction with bulk media, leading to characterisation of both microscopic and macroscopic sources of helicity.

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Bittencourt, Victor A. S. V., Alex E. Bernardini, and Massimo Blasone. "Lepton-Antineutrino Entanglement and Chiral Oscillations." Universe 7, no. 8 (August 9, 2021): 293. http://dx.doi.org/10.3390/universe7080293.

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Dirac bispinors belong to an irreducible representation of the complete Lorentz group, which includes parity as a symmetry yielding two intrinsic discrete degrees of freedom: chirality and spin. For massive particles, chirality is not dynamically conserved, which leads to chiral oscillations. In this contribution, we describe the effects of this intrinsic structure of Dirac bispinors on the quantum entanglement encoded in a lepton-antineutrino pair. We consider that the pair is generated through weak interactions, which are intrinsically chiral , such that in the initial state the lepton and the antineutrino have definite chirality but their spins are entangled. We show that chiral oscillations induce spin entanglement oscillations and redistribute the spin entanglement to chirality-spin correlations. Such a phenomenon is prominent if the momentum of the lepton is comparable with or smaller than its mass. We further show that a Bell-like spin observable exhibits the same behavior of the spin entanglement. Such correlations do not require the knowledge of the full density matrix. Our results show novel effects of the intrinsic bispinor structure and can be used as a basis for designing experiments to probe chiral oscillations via spin correlation measurements.

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15

Ren, Fang-Qin, Fu-Qiang Zhang, Ya-Fen Li, Jin Lv, and Wen-Jin Ma. "Density functional study of the structural, stability, magnetic properties and chirality of small-sized AlxZry (x+y≤9) alloy clusters." Journal of Theoretical and Computational Chemistry 16, no. 07 (November 2017): 1750058. http://dx.doi.org/10.1142/s0219633617500584.

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The equilibrium structures, stabilities, magnetic, and spectroscopic properties of small-sized AlxZry ([Formula: see text]) alloy clusters have been systematically investigated within the framework of density functional theory. We found that the structures of bimetallic clusters prefer to form the same motif as their corresponding pure Al or Zr clusters and chirality turns up in mixed clusters with [Formula: see text] and 9. Computations of VCD and VROA spectra confirmed the chirality of these clusters. For a given cluster size, the most favorable mixing occurs when the ratio of Al:Zr is approximatively equal to 1. The total magnetic moments depend not only on the configuration but also on the composition of the clusters.

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Sun, Lulu, Ning Li, Ji Ma, and Jingang Wang. "Study on Asymmetric Vibrational Coherent Magnetic Transitions and Origin of Fluorescence in Symmetric Structures." Molecules 28, no. 18 (September 15, 2023): 6645. http://dx.doi.org/10.3390/molecules28186645.

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In this work, the physical mechanisms of three highly efficient circularly polarized luminescent materials are introduced. The UV–vis spectra are plotted; the transition properties of their electrons at the excited states are investigated using a combination of the transition density matrix (TDM) and the charge difference density (CDD); combining the distribution of electron clouds, the essence of charge transfer excitation in three structures is explained. The resonance Raman spectrum of the three structures at the S1 and S2 excited states are calculated. The M, M-4 and M, M-5 structures are found to produce novel chirality by electronic circular dichroism (ECD) spectrum, and the reasons for the chirality of the M, M-4 and M, M-5 structures are discussed by analyzing the density of transition electric/magnetic dipole moments (TEDM/TMDMs) in different orientations. Finally, the Raman optical activity (ROA) of M, M-4, and M, M-5 are calculated, and the spectra are plotted. This study will provide guidance for the application of carbon-based nanomaterials in organic electronic devices, solar cells, and optoelectronics.

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Zhang, Qiang, Zhirong Liu, and Ziqiang Cheng. "Chiral Mechanical Effect of the Tightly Focused Chiral Vector Vortex Fields Interacting with Particles." Nanomaterials 13, no. 15 (August 4, 2023): 2251. http://dx.doi.org/10.3390/nano13152251.

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The coupling of the spin-orbit angular momentum of photons in a focused spatial region can enhance the localized optical field’s chirality. In this paper, a scheme for producing a superchiral optical field in a 4π microscopic system is presented by tightly focusing two counter-propagating spiral wavefronts. We calculate the optical forces and torques exerted on a chiral dipole by the chiral light field and reveal the chiral forces by combining the light field and dipoles. Results indicate that, in addition to the general optical force, particles’ motion would be affected by a chiral force that is directly related to the particle chirality. This chiral mechanical effect experienced by the electromagnetic dipoles excited on a chiral particle could be characterized by the behaviors of chirality density and flux, which are, respectively, associated with the reactive and dissipative components of the chiral forces. This work facilitates the advancement of optical separation and manipulation techniques for chiral particles.

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Kuwahara, Shota, Yuki Kuwahara, and Hisanori Shinohara. "Quantitative Analysis of Isolated Single-Wall Carbon Nanotubes with Their Molar Absorbance Coefficients." Journal of Nanomaterials 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/262940.

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The molar absorbance coefficients of metallic, semiconducting, and (6,5) chirality enriched single-wall carbon nanotubes were evaluated by a spray technique combined with atomic force microscopy. Single-wall carbon nanotubes with isolated and a single predominant electronic type were obtained by using the density-gradient ultracentrifugation technique. In the visible region, all coefficients had similar values around 2–5 × 109/mL mol−1 cm−1, independent of their diameter distribution and the electronic types of single-wall carbon nanotubes, and theεS22/εM11 andεS11/εM11were estimated to be 1.0 and 4.0, respectively. The coefficient strongly depends on the length of single-wall carbon nanotubes, independent of their electronic types and chirality.

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Zhang, Wenyan, Fei Liu, Yingfei Hu, Weimin Yang, Hangmin Guan, Lingyun Hao, and Gongxuan Lu. "Pivotal Role of Chirality in Photoelectrocatalytic (PEC) Water Splitting." Current Chinese Science 1, no. 1 (December 23, 2020): 115–21. http://dx.doi.org/10.2174/2210298101999200819110254.

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For decades, the over-exploitation of fossil fuel has made it urgent to develop alternative energy. Photoelectrochemical (PEC) water splitting is a promising approach to generate hydrogen, which is referred to as the fuel of the future due to its high enthalpy of combustion and zero pollution. Though impressive progress has been made over the years, PEC water splitting efficiency is still far from volume production of hydrogen, and more efforts are required to reduce the overpotential, inhibit the yield of hydrogen peroxide by-product, improve the PEC current density, improve light-harvesting capability, and develop low-cost earth-abundant catalysts. Recently, chirality has shown to play a pivotal role in addressing the issues of PEC water splitting via the effect of chiralinduced spin controlling and chiral-enhanced light harvesting. It is high time to pay attention to the art of chirality in promoting water splitting efficiency. Herein, recent progress in this field is reviewed, the approaches to introducing chirality into photo/electronic catalysts for PEC water splitting are summarized, characterization techniques applied in this research field are summed up, the challenges of chirality-enhanced PEC water splitting are discussed, and based on the present achievements, its bright future is anticipated.

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Wang, Y. K., and P. W. Zhao. "Recent Progress on Nuclear Chirality in Covariant Density Functional Theory." Acta Physica Polonica B Proceedings Supplement 13, no. 3 (2020): 567. http://dx.doi.org/10.5506/aphyspolbsupp.13.567.

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Kung, H. H., R. E. Baumbach, E. D. Bauer, V. K. Thorsmolle, W. L. Zhang, K. Haule, J. A. Mydosh, and G. Blumberg. "Chirality density wave of the "hidden order" phase in URu2Si2." Science 347, no. 6228 (February 12, 2015): 1339–42. http://dx.doi.org/10.1126/science.1259729.

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Kwong, Hoi Kwan, Yaozhun Huang, Yuanye Bao, Miu Ling Lam, and Ting-Hsuan Chen. "Remnant Effects of Culture Density on Cell Chirality After Reseeding." ACS Biomaterials Science & Engineering 5, no. 8 (June 4, 2019): 3944–53. http://dx.doi.org/10.1021/acsbiomaterials.8b01364.

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Liu, Dagang, Shuo Wang, Zhongshi Ma, Donglin Tian, Mingyue Gu, and Fengying Lin. "Structure–color mechanism of iridescent cellulose nanocrystal films." RSC Adv. 4, no. 74 (2014): 39322–31. http://dx.doi.org/10.1039/c4ra06268j.

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Chirality, hydrogen bond interaction and surface charge repulsion among sulfate CNCs have vital impact on the formation of a cholesteric mesogen in a suspension or solidified film. Therefore, changing surface charge density through mechanical disintegration is an effect way to tune the chiroptical properties of iridescent CNC films.

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Rosales, Saúl A., Francisco González, Fernando Moreno, and Yael Gutiérrez. "Non-Absorbing Dielectric Materials for Surface-Enhanced Spectroscopies and Chiral Sensing in the UV." Nanomaterials 10, no. 10 (October 21, 2020): 2078. http://dx.doi.org/10.3390/nano10102078.

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Low-loss dielectric nanomaterials are being extensively studied as novel platforms for enhanced light-matter interactions. Dielectric materials are more versatile than metals when nanostructured as they are able to generate simultaneously electric- and magnetic-type resonances. This unique property gives rise to a wide gamut of new phenomena not observed in metal nanostructures such as directional scattering conditions or enhanced optical chirality density. Traditionally studied dielectrics such as Si, Ge or GaP have an operating range constrained to the infrared and/or the visible range. Tuning their resonances up to the UV, where many biological samples of interest exhibit their absorption bands, is not possible due to their increased optical losses via heat generation. Herein, we report a quantitative survey on the UV optical performance of 20 different dielectric nanostructured materials for UV surface light-matter interaction based applications. The near-field intensity and optical chirality density averaged over the surface of the nanoparticles together with the heat generation are studied as figures of merit for this comparative analysis.

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Petržílka, V., and RL Dewar. "Chirality-dependent Plasma Density Profile Changes from Helicon Wave Ponderomotive Forces." Australian Journal of Physics 48, no. 4 (1995): 691. http://dx.doi.org/10.1071/ph950691.

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It is shown that nonresonant helicon-wave-induced transport may result in significant changes in the plasma density radial profile; this is illustrated using parameters appropriate to the cylindrical experiment BASIL and the toroidal experiment SHEILA. Whereas m = +1 helicon waves induce an inward-directed transport and change the density profile to a more centrally peaked one with a higher density on the axis, m = −1 helicon waves induce an outward-directed transport velocity and change the density profile to a hollow one. This may be the clue to the puzzle as to why m = −1 helicon waves are frequently difficult or impossible to excite, as the plasma column is effectively blown off to the discharge chamber walls by the ponderomotive force density of the waves with this chirality (sense of rotation of the wavevector with respect to the axial or toroidal magnetic field).

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Sasaki, Isao, Ryoichi Nakatani, Tetsuo Yoshida, Keiichi Otaki, Yasushi Endo, Yoshio Kawamura, Masahiko Yamamoto, et al. "Magnetization Chirality of Ni-Fe and Ni-Fe/Mn-Ir Asymmetric Ring Dots for High-Density Memory Cells." Materials Science Forum 512 (April 2006): 171–76. http://dx.doi.org/10.4028/www.scientific.net/msf.512.171.

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The magnetic configurations of Ni-20at%Fe/Hf and Ta/Ni-20at%Fe/Mn-28at%Ir/ Ni-20at%Fe/Ta asymmetric ring dots have been studied. Recently, we proposed that asymmetric ring structures are suitable for magnetic memory cells and then demonstrated that asymmetric structures can control the chirality of the vortical magnetization with in-plane fields. The investigation of the Ni-20at%Fe(20 nm)/Hf(5 nm) asymmetric ring dots for free layers in magnetic memory cells demonstrated that switching fields cause a transition from the vortex state to the onion state that increases as the ring width decreases from 410 nm to 210 nm since a narrow ring has a higher demagnetizing field than that of a wide ring during the transition. The investigation of the Ta(3 nm)/Ni-20at%Fe(15 nm)/Mn-28at%Ir(10 nm)/Ni-20at%Fe(3 nm)/Ta(5 nm) asymmetric ring dots for the pinned layers in magnetic memory cells demonstrated that the chirality of the vortical magnetization is pinned regardless of the magnetic field direction.

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Gorbar, E. V., A. I. Momot, I. V. Rudenok, O. O. Sobol, S. I. Vilchinskii, and I. V. Oleinikova. "Chirality Production during Axion Inflation." Ukrainian Journal of Physics 68, no. 11 (December 18, 2023): 717. http://dx.doi.org/10.15407/ujpe68.11.717.

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We study the generation of a chiral charge during the axion inflation, where the pseudoscalar inflaton field φ couples axially to the electromagnetic field via the term (β/Mp)φ E · B with the dimensionless coupling constant β. To describe the evolution of the electromagnetic field and to determine ⟨E·B⟩ sourcing the chiral asymmetry during the inflation due to the chiral anomaly, we employ the gradient-expansion formalism. It operates with a set of vacuum expectation values of the bilinear electromagnetic functions and allows us to consider the backreaction of generated fields on the inflaton evolution, as well as the Schwinger production of charged fermions. In addition, we assume that the produced fermions thermalize and include the chiral magnetic effect contribution to the electric current given by jCME = e2/(2π2)μ5B, where μ5 is the chiral chemical potential which quantifies the produced chiral asymmetry. Solving a set of equations for the inflaton field, scale factor, quadratic functions of the electromagnetic field, and the chiral charge density (chiral chemical potential), we find that the chirality production is quite efficient leading to the generation of a large chiral chemical potential at the end of the axion inflation.

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Wang, Xiao-xu, Lang Yuan, Cai-xin Jia, Hong-jie Qu, Bai-jian Li, Yu-juan Chi, and Hai-tao Yu. "A combined density functional theory and numerical simulation investigation of levels of chirality transfer and regioselectivity for the radical cyclizations of N-methyl-, N-ethyl- and N-isopropyl-substituted ortho-halo-N-acryloylanilides." New Journal of Chemistry 42, no. 12 (2018): 9783–90. http://dx.doi.org/10.1039/c8nj01102h.

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Talukdar, Keka, and Anil Shantappa. "Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction." International Journal of Nanoscience 15, no. 05n06 (October 2016): 1660009. http://dx.doi.org/10.1142/s0219581x16600097.

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Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

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Zhang, A. Ying. "Advances of Study on the Developments and Applications of Carbon Nanotubes." Applied Mechanics and Materials 597 (July 2014): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amm.597.36.

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Many electronic applications of carbon nanotubes crucially rely on techniques of selectively producing either semiconducting or metallic CNTs, preferably of certain chirality. Several methods of separating semiconducting and metallic CNTs are known, but most of them are not yet suitable for large-scale technological processes. The most efficient method relies on density-gradient ultracentrifugation, which separates surfactant-wrapped nanotubes by the minute difference in their density. This density difference often translates into difference in the nanotube diameter and (semi) conducting properties. Another method of separation uses a sequence of freezing, thawing, and compression of SWNTs embedded in agarose gel.

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Reich, S., and C. Thomsen. "Chirality dependence of the density-of-states singularities in carbon nanotubes." Physical Review B 62, no. 7 (August 15, 2000): 4273–76. http://dx.doi.org/10.1103/physrevb.62.4273.

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Hattne, Johan, and Victor S. Lamzin. "A moment invariant for evaluating the chirality of three-dimensional objects." Journal of The Royal Society Interface 8, no. 54 (August 4, 2010): 144–51. http://dx.doi.org/10.1098/rsif.2010.0297.

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Chirality is an important feature of three-dimensional objects and a key concept in chemistry, biology and many other disciplines. However, it has been difficult to quantify, largely owing to computational complications. Here we present a general chirality measure, called the chiral invariant (CI), which is applicable to any three-dimensional object containing a large amount of data. The CI distinguishes the hand of the object and quantifies the degree of its handedness. It is invariant to the translation, rotation and scale of the object, and tolerant to a modest amount of noise in the experimental data. The invariant is expressed in terms of moments and can be computed in almost no time. Because of its universality and computational efficiency, the CI is suitable for a wide range of pattern-recognition problems. We demonstrate its applicability to molecular atomic models and their electron density maps. We show that the occurrence of the conformations of the macromolecular polypeptide backbone is related to the value of the CI of the constituting peptide fragments. We also illustrate how the CI can be used to assess the quality of a crystallographic electron density map.

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Yu, Ji-Sung, Dae-Yun Kim, Joon Moon, Seong-Hyub Lee, Jun-Young Chang, Duck-Ho Kim, Byoung-Chul Min, and Sug-Bong Choe. "Chirality-dependent roughness of magnetic domain walls." Applied Physics Letters 121, no. 17 (October 24, 2022): 172403. http://dx.doi.org/10.1063/5.0111529.

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Dzyaloshinskii–Moriya interaction (DMI) plays a key role in the formation and stability of chiral magnetic objects, such as skyrmions and chiral domain-walls (DWs), which are used as building blocks of emerging high-density and high-speed devices. Here, we demonstrate that the DMI determines also the roughness of chiral DWs. Such DMI-dependent chiral roughness was observed from magnetic multilayer films of the Pt/Co/Pt heterostructure. Despite the stochastic nature of the DW roughness, the films clearly showed the roughness variation with respect to the DW chirality in balance with the DMI. The present analysis of the DW roughness offers a way to quantitatively determine the DMI-induced effective field as an essential parameter for the stability and dynamic characteristics of chiral DWs.

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Han, Jie, Liujian Qi, Cong Ma, and Wang Gao. "Giant rashba splitting of confined Te chains in nanotubes: the size-, chirality-, and type- effects of nanotubes." Journal of Materials Informatics 2, no. 2 (2022): 6. http://dx.doi.org/10.20517/jmi.2022.08.

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Understanding the coupling between one-dimensional (1D) materials and their protective materials is essential for developing nanodevices. Herein, we investigate the effect of the size, chirality, and type of nanotubes [such as carbon/boron nitride nanotubes (CNTs/BNNTs)] on the atomic and electronic structures of confined Te chains using density functional theory. We find that the optimal configurations of the Te chains confined in CNTs/BNNTs depend strongly on the size of the nanotubes but weakly on their chirality and type. Furthermore, the Te@BNNTs exhibit giant Rashba splitting with a Rashba constant of up to 2.65 eV Å, while the Te@CNTs show no splitting. This is mainly due to the large bandgap of the BNNTs, as well as the enhanced symmetry breaking of the Te chains when confined. Our findings provide a basis for the design of nano spin devices through protective materials.

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Jafari, Mirali, and Anna Dyrdał. "First Principle Study on Electronic and Transport Properties of Finite-Length Nanoribbons and Nanodiscs for Selected Two-Dimensional Materials." Molecules 27, no. 7 (March 29, 2022): 2228. http://dx.doi.org/10.3390/molecules27072228.

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Using the density functional theory, we calculate electronic states of various nanoribbons and nanodiscs formed from selected two-dimensional materials, such as graphene, silicene, and hexagonal boron nitride. The main objective of the analysis is a search for zero-energy states in such systems, which is an important issue as their presence indicates certain topological properties associated with chirality. The analysis is also supported by calculating transport properties.

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Takassa, Rabi, Omar Farkad, El Alami Ibnouelghazi, and Driss Abouelaoualim. "Electronic Properties and Band Gaps of Single-Wall Carbon Nanotubes Using <i>π</i> Orbitals Tight-Binding Model: A Comparative Study with <i>Ab Initio</i> Density Functional Theory." Journal of Nano Research 74 (July 12, 2022): 1–10. http://dx.doi.org/10.4028/p-85523u.

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Semiconducting single-wall carbon nanotubes (SWCNTs) have already emerged as a promising candidate for molecular electronics and photovoltaic applications including solar cells. Any application of semiconducting SWCNTs is primarily related to proper information about its bandgap. In this work, the impact of the chirality indices and diameters of a series of armchair and zigzag SWCNTs on the electronic properties (band gap, electronic band structure and density of states (DOS)) are investigated using semi-empirical π orbitals tight-binding (TB) method. The results indicate that the electronic behaviour of the nanotubes changes according to chirality, the total number of electronic sub-bands gets increased when the chirality increases and Van Hove singularities (VHs) appear in its electronic DOS. We have found that for small diameter tubes (less than 0.8 nm), the calculated band gaps don’t agree with DFT calculations based on ab-initio (LDA and GGA) methods, which shows that the semi-empirical TB method including π orbitals only is not sufficient to give a reasonable description of small nanotubes. All Obtained results are in good agreement with previous studies. Semiconducting SWCNTs used in this study are particularly well-suited for the nanoelectronic devices and optoelectronic applications with their direct bandgap and optical transitions, while metallic SWCNTs are considered to be ideal candidates for variety of future nanoelectronic applications such as nanocircuit interconnects and power transmission cables.

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Beppu, Kazusa, Ziane Izri, Tasuku Sato, Yoko Yamanishi, Yutaka Sumino, and Yusuke T. Maeda. "Edge current and pairing order transition in chiral bacterial vortices." Proceedings of the National Academy of Sciences 118, no. 39 (September 24, 2021): e2107461118. http://dx.doi.org/10.1073/pnas.2107461118.

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Bacterial suspensions show turbulence-like spatiotemporal dynamics and vortices moving irregularly inside the suspensions. Understanding these ordered vortices is an ongoing challenge in active matter physics, and their application to the control of autonomous material transport will provide significant development in microfluidics. Despite the extensive studies, one of the key aspects of bacterial propulsion has remained elusive: The motion of bacteria is chiral, i.e., it breaks mirror symmetry. Therefore, the mechanism of control of macroscopic active turbulence by microscopic chirality is still poorly understood. Here, we report the selective stabilization of chiral rotational direction of bacterial vortices in achiral circular microwells sealed by an oil/water interface. The intrinsic chirality of bacterial swimming near the top and bottom interfaces generates chiral collective motions of bacteria at the lateral boundary of the microwell that are opposite in directions. These edge currents grow stronger as bacterial density increases, and, within different top and bottom interfaces, their competition leads to a global rotation of the bacterial suspension in a favored direction, breaking the mirror symmetry of the system. We further demonstrate that chiral edge current favors corotational configurations of interacting vortices, enhancing their ordering. The intrinsic chirality of bacteria is a key feature of the pairing order transition from active turbulence, and the geometric rule of pairing order transition may shed light on the strategy for designing chiral active matter.

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Chen, Ran, and Chuanfu Luo. "How asymmetric chirality and chain density affect chain stiffness of polymer melts." Computational Materials Science 203 (February 2022): 111071. http://dx.doi.org/10.1016/j.commatsci.2021.111071.

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Ishioka, J., Y. H. Liu, K. Shimatake, T. Kurosawa, K. Ichimura, Y. Toda, M. Oda, and S. Tanda. "Measurement of chirality of charge-density-waves in TiSe2 by using STM." Physica B: Condensed Matter 405, no. 11 (June 2010): S214—S216. http://dx.doi.org/10.1016/j.physb.2009.12.085.

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von Rudorff, Guido Falk, and O. Anatole von Lilienfeld. "Simplifying inverse materials design problems for fixed lattices with alchemical chirality." Science Advances 7, no. 21 (May 2021): eabf1173. http://dx.doi.org/10.1126/sciadv.abf1173.

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Brute-force compute campaigns relying on demanding ab initio calculations routinely search for previously unknown materials in chemical compound space (CCS), the vast set of all conceivable stable combinations of elements and structural configurations. Here, we demonstrate that four-dimensional chirality arising from antisymmetry of alchemical perturbations dissects CCS and defines approximate ranks, which reduce its formal dimensionality and break down its combinatorial scaling. The resulting “alchemical” enantiomers have the same electronic energy up to the third order, independent of respective covalent bond topology, imposing relevant constraints on chemical bonding. Alchemical chirality deepens our understanding of CCS and enables the establishment of trends without empiricism for any materials with fixed lattices. We demonstrate the efficacy for three cases: (i) new rules for electronic energy contributions to chemical bonding; (ii) analysis of the electron density of BN-doped benzene; and (iii) ranking over 2000 and 4 million BN-doped naphthalene and picene derivatives, respectively.

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Taradin, Alexey, and Denis G. Baranov. "Chiral light in single-handed Fabry-Perot resonators." Journal of Physics: Conference Series 2015, no. 1 (November 1, 2021): 012012. http://dx.doi.org/10.1088/1742-6596/2015/1/012012.

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Abstract Chirality is a universal phenomenon that is encountered on many different length scales in nature. Interaction of chiral matter with chiral light results in the effect of circular dichroism, which underlies many techniques of discriminating molecular enantiomers. Enhancing dichroic effects is typically achieved by interfacing chiral matter with various optical resonators. In this context it is important to understand how the eigenmodes of optical cavities relate to the field states with well-defined handedness. Here, we present the model of a single-handedness chiral optical cavity supporting only an eigenmode of a given handedness without the presence of modes of other helicity. Resonant excitation of the cavity with light of appropriate handedness enables formation of a helical standing wave with a uniform chirality density, while the opposite handedness does not cause any resonant effects. Our findings expand the set of tools for investigations of chiral matter and open the door towards studies of chiral electromagnetic vacuum states.

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Бузова, М. А., Д. С. Клюев, М. А. Минкин, А. М. Нещерет, and Ю. В. Соколова. "Решение электродинамической задачи для микрополосковой излучающей структуры с киральной подложкой." Письма в журнал технической физики 44, no. 11 (2018): 80. http://dx.doi.org/10.21883/pjtf.2018.11.46200.17147.

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AbstractWe present a solution of the electrodynamic problem for a microstrip radiating structure with a substrate of a chiral metamaterial using the singular integral representation of the field, which in turn is reduced to a singular integral equation with the Cauchy-type singularity relative to the longitudinal component of the surface current density. Graphs of the current distribution for different types of substrates and the chirality parameters of a substrate are given.

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Chen, Zhao-Hua, and Zun Xie. "A Density Functional Theory Study of New Boron Nanotubes." Zeitschrift für Naturforschung A 72, no. 12 (November 27, 2017): 1145–50. http://dx.doi.org/10.1515/zna-2017-0192.

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AbstractUsing first-principles calculations, a series of new boron nanotubes (BNTs), which show various electronic properties, were theoretically predicted. Stable nanotubes with various chiral vectors and diameters can be formed by rolling up the boron sheet with relative stability [H. Tang and S. I. Beigi, Phys. Rev. B 82, 115412 (2010).]. By increasing the diameter for BNT, the stability is enhanced. The calculated density of states and band structures demonstrate that all the predicted BNTs are metallic, regardless of their diameter and chirality. The multicentre chemical bonds of the relatively stable boron sheet and BNTs are analysed using the deformation electron density. Within our study, the BNTs all have metallic conductive characteristics, in addition to having a low effective quality and high carrier concentration, which are very good nanoconductive material properties and could be combined to form high-power electrodes for lithium-ion batteries such as those used in many modern electronics.

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Nishihara, Taishi, Akira Takakura, Masafumi Shimasaki, Kazunari Matsuda, Takeshi Tanaka, Hiromichi Kataura, and Yuhei Miyauchi. "Empirical formulation of broadband complex refractive index spectra of single-chirality carbon nanotube assembly." Nanophotonics 11, no. 5 (January 12, 2022): 1011–20. http://dx.doi.org/10.1515/nanoph-2021-0728.

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Abstract Assemblies of single-walled carbon nanotubes with a specific chiral structure are promising future optofunctional materials because of their strong light–matter coupling arising from sharp optical resonances of quasi-one-dimensional excitons. Their strong optical resonances, which lie in the infrared-to-visible wavelength region, can be selected by their chiralities, and this selectivity promises a wide range of applications including photonic and thermo-optic devices. However, the broadband complex optical spectra of single-chirality carbon nanotube assemblies are scarce in the literature, which has prevented researchers and engineers from designing devices using them. Here, we experimentally determine broadband complex refractive index spectra of single-chirality carbon nanotube assemblies. Free-standing carbon nanotube membranes and those placed on sapphire substrates were fabricated via filtration of the nanotube solution prepared by the separation method using gel chromatography. Transmission and reflection spectra were measured in the mid-infrared to visible wavelength region, and the complex refractive indices of nanotube assemblies were determined as a function of photon energy. The real and imaginary parts of the refractive indices of the nanotube membrane with a bulk density of 1 g cm−3 at the first subband exciton resonance were determined to be approximately 2.7–3.6 and 1.3i–2.4i, respectively. We propose an empirical formula that phenomenologically describes the complex refractive index spectra of various single-chirality nanotube membranes, which can facilitate the design of photonic devices using carbon nanotubes as the material.

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GIUSCA, CRISTINA E., YANN TISON, and S. RAVI P. SILVA. "INTER-LAYER INTERACTION IN DOUBLE-WALLED CARBON NANOTUBES EVIDENCED BY SCANNING TUNNELING MICROSCOPY AND SPECTROSCOPY." Nano 03, no. 02 (April 2008): 65–73. http://dx.doi.org/10.1142/s1793292008000903.

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Scanning Tunneling Microscopy and Spectroscopy have been used in an attempt to elucidate the electronic structure of nanotube systems containing two constituent shells. Evidence for modified electronic structure due to the inter-layer interaction in double-walled carbon nanotubes is provided by the experimental tunneling spectra and the contribution of the inner tube to the local density of states of the "composite" double-walled system is identified in agreement with previous theoretical calculations. An explicit correlation between the chirality of the two constituent tubes, the inter-wall interaction and the overall electronic structure for double-walled carbon nanotubes, is demonstrated by our experiments, showing that the effect the inner tube has on the overall electronic structure of double-walled nanotubes cannot be neglected, and is key to the opto-electronic properties of the system. We postulate that previous analysis of the opto-electronic properties on multiple-walled carbon nanotubes based purely on the outer layer chirality of the tube needs significant modification based on new understanding brought forth with our analysis.

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Qiu, Shi. "Studying the Chiral Magnetic Effect in Pb-Pb and Xe-Xe collisions using the AVFD model." EPJ Web of Conferences 274 (2022): 02005. http://dx.doi.org/10.1051/epjconf/202227402005.

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Quantum Chromodynamics permits the formation of charge conjugation parity violating domains inside the medium produced in heavy-ion collisions, resulting in an imbalanced quark chirality. With the presence of a strong magnetic field (as strong as 1015 T) produced by the spectator protons in offcentral heavy-ion collisions, this would lead to an electric-charge separation along the direction of the magnetic field, known as the Chiral Magnetic Effect (CME). Experimental searches commonly utilise strategies involving charge-dependent correlators to measure the charge separation. These correlators are, however, dominated by a large background proportional to the elliptic flow v2. This article presents a systematic study of the correlators used experimentally to probe the CME by using the Anomalous Viscous Fluid Dynamics (AVFD) model in Pb-Pb and Xe-Xe collisions at √sNN = 5.02 TeV and √sNN = 5.44 TeV, respectively. The results from AVFD suggest that Xe-Xe collisions are consistent with a background-only scenario and a significant non-zero value of axial current density (imbalanced quark chirality) is required to describe the measurements in Pb-Pb collisions.

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Mohammed Aldawsari, Haya, and Smail Bougouffa. "Exploring Optical Nanofibers for Atom-Photon Hybrid Quantum Systems: Chirality Effects and Optical Forces." Journal of Nanoelectronics and Optoelectronics 18, no. 8 (August 1, 2023): 946–58. http://dx.doi.org/10.1166/jno.2023.3463.

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Recent advancements have revealed the growing effectiveness of optical nanofibers in enabling the implementation of atom-photon hybrid quantum systems. These nanofibers serve as non-intrusive tools for probing cold atoms, offering a unique approach to circumvent the limitations imposed by the Rayleigh domain, thereby achieving increased intensities in a beam of light over long distances. This study investigates the interaction between the atom and light, focusing on the dipole transition in sodium atoms near a nanofiber. Notably, we uncover the influence of the direction of light propagation, known as the optical chirality effect, on the spatial distribution of the steady-state density matrix elements. Furthermore, we examine the optical forces acting on a two-level atom during the 32S1/2 →32P3/2 transition in sodium. Our findings demonstrate that optical chirality’s effect significantly impacts the magnitude of these optical forces. The concept of optical chirality holds great promise for advancing technology and enhancing our understanding of atomic behavior. The numerical results presented in this work are based on experimental parameters within a realistic range.

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Ryzhikov, Maxim R., Irina V. Mirzaeva, Svetlana G. Kozlova, and Yuri V. Mironov. "Chirality and Relativistic Effects in Os3(CO)12." Molecules 26, no. 11 (June 1, 2021): 3333. http://dx.doi.org/10.3390/molecules26113333.

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The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os3(CO)12 with D3h and D3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os3(CO)12 corresponds to the D3 symmetry and thus may be characterized either as left-twisted (D3S) or right-twisted (D3R). The D3S↔D3R transitions occur through the D3h transition state with an activation barrier of ~10–14 kJ/mol. Parity violation energy difference (PVED) between D3S and D3R states equals to ~5 × 10−10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os3} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.

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Jafarova, Vusala N., and Aynur N. Jafarova. "Ferromagnetism in silver-doped single-walled zinc oxide nanotubes." Journal of Physics: Conference Series 2699, no. 1 (February 1, 2024): 012015. http://dx.doi.org/10.1088/1742-6596/2699/1/012015.

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Abstract In this paper, the electronic and magnetic properties of single-walled ZnO:Ag nanotubes with a chirality of (6,0) were investigated. Ab initio simulations were carried out using Atomistic ToolKit computer code implementing density functional theory within the local spin density approximation. To obtain an accurate energy band gap for related systems, we used the Hubbard U semiempirical corrections. The introduction of the Ag atom into the ZnO nanotube structure changes the electronic structure, the energy gap decreases with the silver concentration. The calculated value of total magnetic moments of the Ag-doped single-walled ZnO NT system is 1.0 μB. Our results predict that Ag-doped ZnO NT can be a potential candidate for optoelectronic and spintronic devices.

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Gutierrez, Alberto, James E. Jackson, and Kurt Mislow. "Chirality of the electron density distribution in methyl groups with local C3 symmetry." Journal of the American Chemical Society 107, no. 10 (May 1985): 2880–85. http://dx.doi.org/10.1021/ja00296a008.

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Journal articles on the topic 'Densité de chiralité'

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