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Articles de revues sur le sujet « Nanoscale Symmetry »

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Auteur : Grafiati
Publié le 7 septembre 2023

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1

Shao, Yu-Tsun, et Jian-Min Zuo. « Nanoscale symmetry fluctuations in ferroelectric barium titanate, BaTiO3 ». Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 73, no 4 (19 juillet 2017) : 708–14. http://dx.doi.org/10.1107/s2052520617008496.

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Crystal charge density is a ground-state electronic property. In ferroelectrics, charge is strongly influenced by lattice andvice versa, leading to a range of interesting temperature-dependent physical properties. However, experimental determination of charge in ferroelectrics is challenging because of the formation of ferroelectric domains. Demonstrated here is the scanning convergent-beam electron diffraction (SCBED) technique that can be simultaneously used for imaging ferroelectric domains and identifying crystal symmetry and its fluctuations. Results from SCBED confirm the acentric tetragonal, orthorhombic and rhombohedral symmetry for the ferroelectric phases of BaTiO3. However, the symmetry is not homogeneous; regions of a few tens of nanometres retaining almost perfect symmetry are interspersed in regions of lower symmetry. While the observed highest symmetry is consistent with the displacive model of ferroelectric phase transitions in BaTiO3, the observed nanoscale symmetry fluctuations are consistent with the predictions of the order–disorder phase-transition mechanism.
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2

McGrath, R. « Fabricating novel symmetry nanoscale systems using quasicrystal surfaces ». Acta Crystallographica Section A Foundations of Crystallography 61, a1 (23 août 2005) : c37—c38. http://dx.doi.org/10.1107/s0108767305098405.

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3

Lin-Chung, P. J., et A. K. Rajagopal. « Magnetoplasma oscillations in nanoscale tubules with helical symmetry ». Physical Review B 49, no 12 (15 mars 1994) : 8454–63. http://dx.doi.org/10.1103/physrevb.49.8454.

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4

Lin-Chung, P. J., et A. K. Rajagopal. « Electronic excitations in nanoscale systems with helical symmetry ». Journal of Physics : Condensed Matter 6, no 20 (16 mai 1994) : 3697–706. http://dx.doi.org/10.1088/0953-8984/6/20/009.

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5

Su, Jiaye, Keda Yang et Hongxia Guo. « Asymmetric transport of water molecules through a hydrophobic conical channel ». RSC Adv. 4, no 76 (2014) : 40193–98. http://dx.doi.org/10.1039/c4ra07034h.

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Muller, Eric A., Benjamin Pollard, Hans A. Bechtel, Peter van Blerkom et Markus B. Raschke. « Infrared vibrational nanocrystallography and nanoimaging ». Science Advances 2, no 10 (octobre 2016) : e1601006. http://dx.doi.org/10.1126/sciadv.1601006.

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Molecular solids and polymers can form low-symmetry crystal structures that exhibit anisotropic electron and ion mobility in engineered devices or biological systems. The distribution of molecular orientation and disorder then controls the macroscopic material response, yet it is difficult to image with conventional techniques on the nanoscale. We demonstrated a new form of optical nanocrystallography that combines scattering-type scanning near-field optical microscopy with both optical antenna and tip-selective infrared vibrational spectroscopy. From the symmetry-selective probing of molecular bond orientation with nanometer spatial resolution, we determined crystalline phases and orientation in aggregates and films of the organic electronic material perylenetetracarboxylic dianhydride. Mapping disorder within and between individual nanoscale domains, the correlative hybrid imaging of nanoscale heterogeneity provides insight into defect formation and propagation during growth in functional molecular solids.
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Wang, Chunyan, Dahu Chang, Junfei Wang, Qilong Gao, Yinuo Zhang, Chunyao Niu, Chengyan Liu et Yu Jia. « Size and crystal symmetry breaking effects on negative thermal expansion in ScF3 nanostructures ». Physical Chemistry Chemical Physics 23, no 43 (2021) : 24814–22. http://dx.doi.org/10.1039/d1cp02809j.

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8

Melcher, Christof. « Chiral skyrmions in the plane ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 470, no 2172 (8 décembre 2014) : 20140394. http://dx.doi.org/10.1098/rspa.2014.0394.

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Magnets without inversion symmetry are a prime example of a solid-state system featuring topological solitons on the nanoscale, and a promising candidate for novel spintronic applications. Magnetic chiral skyrmions are localized vortex-like structures, which are stabilized by antisymmetric exchange interaction, the so-called Dzyaloshinskii–Moriya interaction. In continuum theories, the corresponding energy contribution is, in contrast to the classical Skyrme mechanism from nuclear physics, of linear gradient dependence and breaks the chiral symmetry. In the simplest possible case of a ferromagnetic energy in the plane, including symmetric and antisymmetric exchange and Zeeman interaction, we show that the least energy in a class of fields with unit topological charge is attained provided the Zeeman field is sufficiently large.
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9

Borodin, Y. V., K. V. Sysolov, V. R. Rande, G. V. Vavilova et O. Starý. « Spectroscopy of nanoscale crystalline structural elements ». Bulletin of the Karaganda University. "Physics" Series 99, no 3 (30 septembre 2020) : 46–53. http://dx.doi.org/10.31489/2020ph3/46-53.

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The study of structural elements, nanoparticles, microblocks and other nanoscale objects was an important part of the study of crystals non-equilibrium properties. The behavior of nanoscale structures allows us to judge the dynamics of the crystal lattice during doping, deformation, and interactions with radiation. Along with x-ray and electron microscopic studies, optical methods for determining the size of nanoscale objects, the energy of their electrons, and the symmetry of electronic States are increasingly being used. Among nanoscale objects, proton-separated structural elements (PSE) attract special attention in connection with the development of crystal structure block-hierarchical (BH) model. In this paper, we consider the possibility of calculating the size of PSE crystals in a model of quantum-dimensional structures. According to this model except values of the crystal potential in PSE, you should consider the area of high electron density, the existence of which is beyond the scope of conventional theory. Experimental data allow us to determine the position of this zone as localized around the atomic core of the PSE. Note that the atomic backbone generally coincides with the unit cell, that is, it consists of the same number of atoms and has the same point symmetry group.
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10

Park, Jun-Hee, Abdoulaye Ndao, Wei Cai, Liyi Hsu, Ashok Kodigala, Thomas Lepetit, Yu-Hwa Lo et Boubacar Kanté. « Symmetry-breaking-induced plasmonic exceptional points and nanoscale sensing ». Nature Physics 16, no 4 (17 février 2020) : 462–68. http://dx.doi.org/10.1038/s41567-020-0796-x.

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11

Waldvogel, Siegfried R., Alexander R. Wartini, Palle H. Rasmussen et Julius Rebek. « A triphenylene scaffold with C3v-symmetry and nanoscale dimensions ». Tetrahedron Letters 40, no 18 (avril 1999) : 3515–18. http://dx.doi.org/10.1016/s0040-4039(99)00545-6.

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12

Grutter, A. J., A. Vailionis, J. A. Borchers, B. J. Kirby, C. L. Flint, C. He, E. Arenholz et Y. Suzuki. « Interfacial Symmetry Control of Emergent Ferromagnetism at the Nanoscale ». Nano Letters 16, no 9 (8 août 2016) : 5647–51. http://dx.doi.org/10.1021/acs.nanolett.6b02255.

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13

Tagantsev, Alexander K., Vincent Meunier et Pradeep Sharma. « Novel Electromechanical Phenomena at the Nanoscale : Phenomenological Theory and Atomistic Modeling ». MRS Bulletin 34, no 9 (septembre 2009) : 643–47. http://dx.doi.org/10.1557/mrs2009.175.

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AbstractIn the past two decades, the fact that “small is different” has been established for a wide variety of phenomena, including electrical, optical, magnetic, and mechanical behavior of materials. However, one largely untapped but potentially very important area of nanoscience involves the interplay of electricity and mechanics at the nanoscale. In this article, predicated on both phenomenological approaches and atomistic calculations, we summarize the state-of-the-art in understanding electromechanical coupling at the nanoscale. First, we address flexoelectricity—the coupling of strain gradient to polarization. Flexoelectricity exists in both piezoelectric and nonpiezoelectric dielectrics. As a high-order spatial-dispersion effect, the flexoelectricity becomes more and more important with the reduction of the spatial scale of the problem. Exploitation of this phenomenon and the associated nanoscale size effects can lead to tantalizing applications, such as “piezoelectric nanocomposites without using piezoelectric materials.” The second issue concerns electromechanical effects at the dielectric/metal interface. An interface in solids typically exhibits a lower symmetry compared to that of the associated adhering materials. This symmetry reduction can drastically affect the electromechanical and dielectric behavior of the material at the nanoscale.
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14

Guo, Er-Jia, Ryan Desautels, David Keavney, Manuel A. Roldan, Brian J. Kirby, Dongkyu Lee, Zhaoliang Liao et al. « Nanoscale ferroelastic twins formed in strained LaCoO3 films ». Science Advances 5, no 3 (mars 2019) : eaav5050. http://dx.doi.org/10.1126/sciadv.aav5050.

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The coexistence and coupling of ferroelasticity and magnetic ordering in a single material offers a great opportunity to realize novel devices with multiple tuning knobs. Complex oxides are a particularly promising class of materials to find multiferroic interactions due to their rich phase diagrams, and are sensitive to external perturbations. Still, there are very few examples of these systems. Here, we report the observation of twin domains in ferroelastic LaCoO3 epitaxial films and their geometric control of structural symmetry intimately linked to the material’s electronic and magnetic states. A unidirectional structural modulation is achieved by selective choice of substrates having twofold rotational symmetry. This modulation perturbs the crystal field–splitting energy, leading to unexpected in-plane anisotropy of orbital configuration and magnetization. These findings demonstrate the use of structural modulation to control multiferroic interactions and may enable a great potential for stimulation of exotic phenomena through artificial domain engineering.
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15

ANTONIAK, C., et M. FARLE. « MAGNETISM AT THE NANOSCALE : THE CASE OF FePt ». Modern Physics Letters B 21, no 18 (10 août 2007) : 1111–31. http://dx.doi.org/10.1142/s0217984907013821.

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Fe x Pt 1-x nanoparticles prepared by organometallic synthesis and gas-phase condensation were structurally and magnetically characterised. The effective spin magnetic moments at both the Fe and Pt sites are reduced with respect to the moments in the corresponding bulk material by up to 20% and further decrease with decreasing particle size at the Fe sites. The ratio of orbital-to-effective-spin magnetic moment [Formula: see text] at the Fe sites increases from 2.1% for 6 nm particles to 3.4% for 3.4 nm particles due to the break of symmetry at the surface. A lowering of the crystal symmetry after the transformation to the chemically ordered L1 0 state yields a [Formula: see text] ≈ 9% and is accompanied by an enhancement of the coercive field at 15 K from (36±5) mT to (292±8) mT indicating an increase of the anisotropy.
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16

Choe, Wonyoung, A. O. Pecharsky, Michael Wörle et Gordon J. Miller. « “Nanoscale Zippers” in Gd5(SixGe1-x)4 : Symmetry and Chemical Influences on the Nanoscale Zipping Action ». Inorganic Chemistry 42, no 25 (décembre 2003) : 8223–29. http://dx.doi.org/10.1021/ic034941z.

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17

Curtis, A. S. G., N. Gadegaard, M. J. Dalby, M. O. Riehle, C. D. W. Wilkinson et G. Aitchison. « Cells React to Nanoscale Order and Symmetry in Their Surroundings ». IEEE Transactions on Nanobioscience 3, no 1 (mars 2004) : 61–65. http://dx.doi.org/10.1109/tnb.2004.824276.

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18

Parreiras, S. O., M. Gastaldo, C. Moreno, M. D. Martins, A. Garcia-Lekue, G. Ceballos, R. Paniago et A. Mugarza. « Symmetry forbidden morphologies and domain boundaries in nanoscale graphene islands ». 2D Materials 4, no 2 (22 mai 2017) : 025104. http://dx.doi.org/10.1088/2053-1583/aa70fa.

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19

Alves, Cassio, Jan Skov Pedersen et Cristiano Luis Pinto Oliveira. « Modelling of high-symmetry nanoscale particles by small-angle scattering ». Journal of Applied Crystallography 47, no 1 (7 décembre 2013) : 84–94. http://dx.doi.org/10.1107/s1600576713028549.

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A versatile procedure to build high-symmetry objects and to calculate their corresponding small-angle scattering intensity is presented. Starting from a set of vertex positions, available from a large and extensible database, it is possible to build several types of bodies using spherical subunits. A fast implementation, based on the Debye formula using a histogram of distance, is then used to compute the theoretical scattering intensity. Since the model is built from the definition of a small set of parameters, it is possible to perform an optimization of structural parameters against experimental data. Finally, affine size polydispersities can be easily included by the rescaling of the histogram of the positions used in the calculations. Several examples of the calculations are presented, demonstrating the method and its applicability.
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20

Longuinhos, R., et J. Ribeiro-Soares. « Ultra-weak interlayer coupling in two-dimensional gallium selenide ». Physical Chemistry Chemical Physics 18, no 36 (2016) : 25401–8. http://dx.doi.org/10.1039/c6cp03806a.

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By using symmetry arguments and first principles calculations, we study the stability of β and ε few-layer GaSe and their low-frequency interlayer breathing and shear modes, unveiling uncommon lubricant properties and exfoliability at the nanoscale.
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21

Lookman, Turab, et Peter Littlewood. « Nanoscale Heterogeneity in Functional Materials ». MRS Bulletin 34, no 11 (novembre 2009) : 822–31. http://dx.doi.org/10.1557/mrs2009.232.

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AbstractThe physical properties that make “functional” materials worthy of their moniker frequently arise because of a phase transition that establishes a new kind of order as the material is cooled from a parent state. Such ordered states include ferroelectrics, ferromagnets, and structurally ordered martensites; because these states all break an orientational symmetry, and it is rare that one can produce the conditions for single domain crystallinity, the observed configuration is generally heterogeneous. However, the conditions under which domain structures form are highly constrained, especially by elastic interactions within a solid; consequently, the observed structures are far from fully random, even if disorder is present. Often the structure of the heterogeneity is important to the function, as in shape-memory alloys. Increasingly, we are surprised to discover new phases inside solids that are themselves a heterogeneous modulation of their parents.
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22

Kim, Kyou-Hyun, David A. Payne et Jian Min Zuo. « Determination of fluctuations in local symmetry and measurement by convergent beam electron diffraction : applications to a relaxor-based ferroelectric crystal after thermal annealing ». Journal of Applied Crystallography 46, no 5 (18 septembre 2013) : 1331–37. http://dx.doi.org/10.1107/s0021889813022097.

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Single crystals of Pb(Mg1/3Nb2/3)O3–31%PbTiO3(PMN–31%PT) are known for their complex domain structures at the nanometre scale. While their average symmetry has been studied by X-ray, neutron and electron diffraction methods, there is little knowledge about variations in symmetry at the local scale. Here, direct evidence is provided for the volume dependence and spatial dependence of symmetry fluctuations by using quantitative convergent beam electron diffraction and energy dispersive X-ray spectroscopy. Fluctuations in symmetry were determined by using different electron beam probe sizes ranging from ∼2 to 25 nm from a crystal ∼62 nm thick. The symmetry of PMN–31%PT was found to increase linearly as the average volume increased, and the local symmetry fluctuated from one location to another at the nanoscale. Energy dispersive X-ray spectroscopy indicates that chemical fluctuations are significant when the probe size decreases to ∼2 nm. The symmetry fluctuation is attributed to locally varying composition-dependent ionic displacements and spontaneous polarization.
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Cho, Junhan. « Identification of Some New Triply Periodic Mesophases from Molten Block Copolymers ». Polymers 11, no 6 (25 juin 2019) : 1081. http://dx.doi.org/10.3390/polym11061081.

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Using field-theoretic simulations based on a self-consistent field theory (SCFT) with or without finite compressibility, nanoscale mesophase formation in molten linear AB and ABC block copolymers is investigated in search of candidates for new and useful nanomaterials. At selected compositions and segregation strengths, the copolymers are shown to evolve into some new nanostructures with either unusual crystal symmetry or a peculiar morphology. There exists a holey layered morphology with Im3 symmetry, which lacks one mirror reflection compared with Im3m symmetry. Also, a peculiar cubic bicontinuous morphology, whose channels are connected with tetrapod units, is found to have Pn3m symmetry. It is shown that there is another network morphology with tripod connections, which reveals P432 symmetry. The optimized free energies of these new mesophases and their relative stability are discussed in comparison with those of double gyroids and double diamonds.
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Barbillon, Grégory, Andrey Ivanov et Andrey K. Sarychev. « Applications of Symmetry Breaking in Plasmonics ». Symmetry 12, no 6 (1 juin 2020) : 896. http://dx.doi.org/10.3390/sym12060896.

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Plasmonics is one of the most used domains for applications to optical devices, biological and chemical sensing, and non-linear optics, for instance. Indeed, plasmonics enables confining the electromagnetic field at the nanoscale. The resonances of plasmonic systems can be set in a given domain of a spectrum by adjusting the geometry, the spatial arrangement, and the nature of the materials. Moreover, symmetry breaking can be used for the further improvement of the optical properties of the plasmonic systems. In the last three years, great advances in or insights into the use of symmetry breaking in plasmonics have occurred. In this mini-review, we present recent insights and advances on the use of symmetry breaking in plasmonics for applications to chemistry, sensing, devices, non-linear optics, and chirality.
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25

FJELDLY, TOR A., et UDIT MONGA. « PHYSICS BASED ANALYTICAL MODELING OF NANOSCALE MULTIGATE MOSFETs ». International Journal of High Speed Electronics and Systems 22, no 01 (novembre 2013) : 1350003. http://dx.doi.org/10.1142/s0129156413500031.

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Various physics based modeling schemes for multigate MOSFETs are presented. In all cases, the models are derived from an analysis of the device body electrostatics in terms of two- or three-dimensional Laplace's and Poisson's equations, where short-channel and scaling effects are implicitly accounted for. Thus a comprehensive modeling framework is derived for the subthreshold electrostatics of double-gate MOSFETs based on a conformal mapping analysis of the potential distribution in the device body arising from the inter-electrode capacitive coupling. This technique is also applied to the circular gate-all-around MOSFET by utilizing the symmetry properties of this device. For both these devices, the modeling is extended to include the strong inversion regime by a self-consistent procedure that simultaneously allows the calculation of the quasi-Fermi potential distribution, the drain current, and the intrinsic capacitances. In an alternative modeling framework, covering a wide range of multigate devices in a unified manner, the potential distribution is derived from a select set of isomorphic trial functions that reflect the geometry and symmetry properties of the devices. Modeling parameters used are self-consistently determined by imposing boundary conditions associated with Laplace's or Poisson's equation. Finally, the effects of quantum mechanical confinement are discussed for ultra thin body devices. The results of the modeling are in excellent agreement with numerical simulations.
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Powers-Riggs, Natalia E., Xiaobing Zuo, Ryan M. Young et Michael R. Wasielewski. « Symmetry-Breaking Charge Separation in a Nanoscale Terrylenediimide Guanine-Quadruplex Assembly ». Journal of the American Chemical Society 141, no 44 (24 octobre 2019) : 17512–16. http://dx.doi.org/10.1021/jacs.9b10108.

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Hu, Lei, Feiyu Qin, Andrea Sanson, Liang-Feng Huang, Zhao Pan, Qiang Li, Qiang Sun et al. « Localized Symmetry Breaking for Tuning Thermal Expansion in ScF3 Nanoscale Frameworks ». Journal of the American Chemical Society 140, no 13 (20 mars 2018) : 4477–80. http://dx.doi.org/10.1021/jacs.8b00885.

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Kleemann, W., A. Albertini, M. Kuss et R. Lindner. « Optical detection of symmetry breaking on a nanoscale in SrTiO3:Ca ». Ferroelectrics 203, no 1 (novembre 1997) : 57–74. http://dx.doi.org/10.1080/00150199708012832.

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Samulski, Edward T., Denisse Reyes-Arango, Alexandros G. Vanakaras et Demetri J. Photinos. « All Structures Great and Small : Nanoscale Modulations in Nematic Liquid Crystals ». Nanomaterials 12, no 1 (29 décembre 2021) : 93. http://dx.doi.org/10.3390/nano12010093.

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The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular organization is incomplete and poorly understood. One attempt to explain nanoscale phenomena merely “shrinks down” established macroscopic continuum elasticity modeling. That explanation initially (and mistakenly) identified the low temperature nematic phase (NX), first observed in symmetric mesogenic dimers of the CB-n-CB series with an odd number of methylene spacers (n), as a twist–bend nematic (NTB). We show that the NX is unrelated to any of the elastic deformations (bend, splay, twist) stipulated by the continuum elasticity theory of nematics. Results from molecular theory and computer simulations are used to illuminate the local symmetry and physical origins of the nanoscale modulations in the NX phase, a spontaneously chiral and locally polar nematic. We emphasize and contrast the differences between the NX and theoretically conceivable nematics exhibiting spontaneous modulations of the elastic modes by presenting a coherent formulation of one-dimensionally modulated nematics based on the Frank–Oseen elasticity theory. The conditions for the appearance of nematic phases presenting true elastic modulations of the twist–bend, splay–bend, etc., combinations are discussed and shown to clearly exclude identifications with the nanoscale-modulated nematics observed experimentally, e.g., the NX phase. The latter modulation derives from packing constraints associated with nonlinear molecules—a chiral, locally-polar structural organization indicative of a new type of nematic phase.
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Planes, Antoni, Pol Lloveras, Teresa Castán, Marcel Porta et Avadh Saxena. « Precursor Nanoscale Textures : from Tweed to Glassy Behaviour ». Solid State Phenomena 172-174 (juin 2011) : 135–43. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.135.

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We study spatially inhomogeneous states that occur as precursors of marten-sitic/ferroelastic transitions. We will show that cross-hatched modulations (tweed patterns)arise at temperatures above the phase transition in the limit of high elastic anisotropy or lowdisorder while a nano-cluster phase-separated state occurs at low anisotropy or high disorder.In the latter case, nanoscale inhomogeneities give rise to glassy behaviour while the structuraltransition is inhibited. Interestingly, in this case the ferroelastic system also displays a largethermo-mechanical response so that the low symmetry structure can be easily induced by theapplication of relatively small stresses within a broad temperature range.
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Dalby, Matthew J., Nikolaj Gadegaard, Rahul Tare, Abhay Andar, Mathis O. Riehle, Pawel Herzyk, Chris D. W. Wilkinson et Richard O. C. Oreffo. « The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder ». Nature Materials 6, no 12 (23 septembre 2007) : 997–1003. http://dx.doi.org/10.1038/nmat2013.

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32

Lu, Fang, Thi Vo, Yugang Zhang, Alex Frenkel, Kevin G. Yager, Sanat Kumar et Oleg Gang. « Unusual packing of soft-shelled nanocubes ». Science Advances 5, no 5 (mai 2019) : eaaw2399. http://dx.doi.org/10.1126/sciadv.aaw2399.

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Space-filling generally governs hard particle packing and the resulting phases and interparticle orientations. Contrastingly, hard-shaped nanoparticles with grafted soft-ligands pack differently since the energetically interacting soft-shell is amenable to nanoscale sculpturing. While the interplay between the shape and soft-shell can lead to unforeseen packing effects, little is known about the underlying physics. Here, using electron microscopy and small-angle x-ray scattering, we demonstrate that nanoscale cubes with soft, grafted DNA shells exhibit remarkable packing, distinguished by orientational symmetry breaking of cubes relative to the unit cell vectors. This zigzag arrangement occurs in flat body-centered tetragonal and body-centered cubic phases. We ascribe this unique arrangement to the interplay between shape and a spatially anisotropic shell resulting from preferential grafting of ligands to regions of high curvature. These observations reveal the decisive role played by shell-modulated anisotropy in nanoscale packing and suggest a plethora of new spatial organizations for molecularly decorated shaped nanoparticles.
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Kumar, Ashok, et Hitesh Borkar. « Flexoelectricity in Bulk and Nanoscale Polar and Non-Polar Dielectrics ». Solid State Phenomena 232 (juin 2015) : 213–33. http://dx.doi.org/10.4028/www.scientific.net/ssp.232.213.

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Piezoelectricity (PE) is defined as the polarization under homogeneous application of stress on polar/non-centrosymmetry/no-inversion symmetry dielectrics, whereas it has been commonly accepted that flexoelectricity (FLX) is the induced polarization due to strain gradient in any polar/nonpolar dielectrics, the latter effect is universal and can be generated in any materials under inhomogeneous stress. Flexoelectricity is inversely proportional to the size of materials and devices which further suggests that giant FLX effects may develop in nanoscale materials. Flexoelectricity represents the polarization due to strain gradient and have significant effects on the functional properties of nanoscale materials, epitaxial thin films, one-dimensional structure with various shape and size, liquid crystals, polymers, nanobio-hybrid materials, etc. Till late sixties, very few works on flexoelectricity have been reported due to very weak magnitude compared to piezoelectricity. Advancement in nanoscale materials and device fabrication process and highly sophisticated electronics with detection of data with high signal to noise ratio lead the scientists/researchers to get several orders of higher flexoelectric coefficients compared to the proposed theoretical limits. Recently, giant FLX have been observed in nanoscale materials and their magnitudes are six to seven orders larger than the theoretical limits. In this review article, we describe the basic mechanism of flexoelectricity, brief history of discovery, theoretical modeling, experimental procedures, and results reported by several authors for bulk and nanoscale ferroelectric and dielectric materials.
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Tomalia, Donald A., Linda S. Nixon et David M. Hedstrand. « The Role of Branch Cell Symmetry and Other Critical Nanoscale Design Parameters in the Determination of Dendrimer Encapsulation Properties ». Biomolecules 10, no 4 (21 avril 2020) : 642. http://dx.doi.org/10.3390/biom10040642.

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This article reviews progress over the past three decades related to the role of dendrimer-based, branch cell symmetry in the development of advanced drug delivery systems, aqueous based compatibilizers/solubilizers/excipients and nano-metal cluster catalysts. Historically, it begins with early unreported work by the Tomalia Group (i.e., The Dow Chemical Co.) revealing that all known dendrimer family types may be divided into two major symmetry categories; namely: Category I: symmetrical branch cell dendrimers (e.g., Tomalia, Vögtle, Newkome-type dendrimers) possessing interior hollowness/porosity and Category II: asymmetrical branch cell dendrimers (e.g., Denkewalter-type) possessing no interior void space. These two branch cell symmetry features were shown to be pivotal in directing internal packing modes; thereby, differentiating key dendrimer properties such as densities, refractive indices and interior porosities. Furthermore, this discovery provided an explanation for unimolecular micelle encapsulation (UME) behavior observed exclusively for Category I, but not for Category II. This account surveys early experiments confirming the inextricable influence of dendrimer branch cell symmetry on interior packing properties, first examples of Category (I) based UME behavior, nuclear magnetic resonance (NMR) protocols for systematic encapsulation characterization, application of these principles to the solubilization of active approved drugs, engineering dendrimer critical nanoscale design parameters (CNDPs) for optimized properties and concluding with high optimism for the anticipated role of dendrimer-based solubilization principles in emerging new life science, drug delivery and nanomedical applications.
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Venturi, L., L. Rigutti, J. Houard, I. Blum, S. Malykhin, A. Obraztsov et A. Vella. « Strain sensitivity and symmetry of 2.65 eV color center in diamond nanoscale needles ». Applied Physics Letters 114, no 14 (8 avril 2019) : 143104. http://dx.doi.org/10.1063/1.5092329.

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LaFave, Tim, et Raphael Tsu. « Capacitance : A property of nanoscale materials based on spatial symmetry of discrete electrons ». Microelectronics Journal 39, no 3-4 (mars 2008) : 617–23. http://dx.doi.org/10.1016/j.mejo.2007.07.105.

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Kuchibhatla, Satyanarayana V. N. T., A. S. Karakoti, D. C. Sayle, H. Heinrich et S. Seal. « Symmetry-Driven Spontaneous Self-Assembly of Nanoscale Ceria Building Blocks to Fractal Superoctahedra ». Crystal Growth & ; Design 9, no 3 (4 mars 2009) : 1614–20. http://dx.doi.org/10.1021/cg801358z.

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Rocha, Marisa A. A., Catarina M. S. S. Neves, Mara G. Freire, Olga Russina, Alessandro Triolo, João A. P. Coutinho et Luís M. N. B. F. Santos. « Alkylimidazolium Based Ionic Liquids : Impact of Cation Symmetry on Their Nanoscale Structural Organization ». Journal of Physical Chemistry B 117, no 37 (4 septembre 2013) : 10889–97. http://dx.doi.org/10.1021/jp406374a.

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Zhang, Longyan, Jinliang Xu, Junpeng Lei et Guanglin Liu. « The connection between wall wettability, boiling regime and symmetry breaking for nanoscale boiling ». International Journal of Thermal Sciences 145 (novembre 2019) : 106033. http://dx.doi.org/10.1016/j.ijthermalsci.2019.106033.

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Bozin, Emil, Kevin Knox, Pavol Juhas, Yew San Hor, John Mitchell et Simon Billinge. « Nanoscale phase coexistence at the metal-insulator transition in Cu(Ir1–xCrx)2S4 ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1351. http://dx.doi.org/10.1107/s2053273314086483.

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Increasingly, nanoscale phase coexistence and hidden broken symmetry states are being found in the vicinity of metal-insulator transitions (MIT), for example, in high temperature superconductors, heavy fermion and colossal magnetoresistive materials, but their importance and possible role in the MIT and related emergent behaviors is not understood. Despite their ubiquity, they are hard to study because they produce weak diffuse signals in most measurements. Here we propose Cu(Ir1–xCrx)2S4 as a model system for studying nanoscale phase coexistence at the MIT, where robust local structural signals lead to key new insights. We demonstrate by x-ray scattering measurements and atomic pair distribution function approach a hitherto unobserved coexistence of a Ir4+ charge-localized dimer phase and Cr-ferromagnetism. The resulting phase diagram that takes into account the short range dimer order, is highly reminiscent of a generic MIT phase diagram similar to the cuprates. The results represent the first observation of nanoscale phase coexistence in iridates [1]. We suggest that the presence of quenched strain from dopant ions acts as an arbiter deciding between the competing ground states.
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Li Voti, Roberto, Grigore Leahu, Emilija Petronijevic, Alessandro Belardini, Tiziana Cesca, Carlo Scian, Giovanni Mattei et Concita Sibilia. « Characterization of Chirality in Diffractive Metasurfaces by Photothermal Deflection Technique ». Applied Sciences 12, no 3 (21 janvier 2022) : 1109. http://dx.doi.org/10.3390/app12031109.

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Chirality, a lack of mirror symmetry, is present in nature at all scales; at the nanoscale, it governs the biochemical reactions of many molecules, influencing their pharmacology and toxicity. Chiral substances interact with left and right circularly polarized light differently, but this difference is very minor in natural materials. Specially engineered, nanostructured, periodic materials can enhance the chiro-optical effects if the symmetry in their interactions with circular polarization is broken. In the diffraction range of such metasurfaces, the intensity of diffracted orders depends on the chirality of the input beam. In this work, we combine a photothermal deflection experiment with a novel theoretical framework to reconstruct both the thermal and optical behavior of chiro-optical behavior in diffracted beams.
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Tirry, Wim, Dominique Schryvers, Kevin Jorissen et Dirk Lamoen. « Electron-diffraction structure refinement of Ni4Ti3 precipitates in Ni52Ti48 ». Acta Crystallographica Section B Structural Science 62, no 6 (14 novembre 2006) : 966–71. http://dx.doi.org/10.1107/s0108768106036457.

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The atomic coordinates of the crystal structure of nanoscale Ni4Ti3 precipitates in Ni-rich NiTi is refined by means of a least-squares method based on intensity measures of electron-diffraction patterns. The optimization is performed in combination with density functional theory calculations and has yielded an R\bar 3 symmetry with slightly different atomic positions when compared with the existing structure. The new unit cell offers a better understanding of the lattice deformation from the B2 matrix.
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Gavrichkov, Vladimir A., et Semyon I. Polukeev. « Magnetic Interaction in Doped 2D Perovskite Cuprates with Nanoscale Inhomogeneity : Lattice Nonlocal Effects vs. Superexchange ». Condensed Matter 7, no 4 (18 octobre 2022) : 57. http://dx.doi.org/10.3390/condmat7040057.

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We have studied the superexchange interaction Jij in doped 2D cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO2 layer surrounded by two LaO rock salt layers. In a static U and D stripe nanostructure, the homogeneous AFM interaction is impossible due to the U/D/U… periodic stripe sequence and TN=0. In a dynamic stripe nanostructure, the ideal CuO2 layer with nonlocal effects and the homogeneous AFM interaction are restored. However, the interaction Jij decreases by the exponential factor due to partial dynamic quenching. The meaning of the transition from the dynamic to the static cases lies in the spontaneous θ-symmetry breaking with respect to the rotation of all the tilted CuO6 octahedra by an orientation angle δθ=n·45° (where n=1÷4) in the U and D stripe nanostructure of the CuO2 layer. Moreover, the structural features help to study various experimental data on the charge inhomogeneity, Fermi level pinning in the p type cuprates only and time reversal symmetry breaking from a unified point of view.
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Mahmoud, Mahmoud A., Daniel O’Neil et Mostafa A. El-Sayed. « Shape- and Symmetry-Dependent Mechanical Properties of Metallic Gold and Silver on the Nanoscale ». Nano Letters 14, no 2 (22 janvier 2014) : 743–48. http://dx.doi.org/10.1021/nl4040362.

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Nagai, Yuki, Yukihiro Ota et K. Tanaka. « Time-reversal symmetry breaking phase and gapped surface states in d-wave nanoscale superconductors ». Journal of Physics : Conference Series 969 (mars 2018) : 012039. http://dx.doi.org/10.1088/1742-6596/969/1/012039.

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Di Sia, Paolo. « Symmetry and the Nanoscale : Advances in Analytical Modeling in the Perspective of Holistic Unification ». Symmetry 15, no 8 (21 août 2023) : 1611. http://dx.doi.org/10.3390/sym15081611.

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Analytical modeling presents symmetries and aesthetic-mathematical characteristics which are not catchable in numerical computation for science and technology; nanoscience plays a significant role in unification attempts, considering also models including holistic aspects of reality. In this paper we present new discovered results about the complete analytical quantum-relativistic form of the mean square deviation of position R2(t) related to a recently introduced Drude–Lorentz-like model (DS model), already performed at classical, quantum and relativistic level. The function R2(t) gives precise information about the distance crossed by carriers (electrons, ions, etc.) inside a nanostructure, considering both quantum effects and relativistic velocities. The model has a wide scale range of applicability; the nanoscale is considered in this paper, but it holds application from sub-pico-level to macro-level because of the existence of a gauge factor, making it applicable to every oscillating process in nature. Examples of application and suggestions supplement this paper, as well as interesting developments to be studied related to the model and to one of the basic elements of a current unified holistic approach based on vacuum energy.
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Xu, Xiaofeng, Xiao-Qing Luo, Qinke Liu, Yan Li, Weihua Zhu, Zhiyong Chen, Wuming Liu et Xin-Lin Wang. « Plasmonic Sensing and Switches Enriched by Tailorable Multiple Fano Resonances in Rotational Misalignment Metasurfaces ». Nanomaterials 12, no 23 (28 novembre 2022) : 4226. http://dx.doi.org/10.3390/nano12234226.

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Fano resonances that feature strong field enhancement in the narrowband range have motivated extensive studies of light–matter interactions in plasmonic nanomaterials. Optical metasurfaces that are subject to different mirror symmetries have been dedicated to achieving nanoscale light manipulation via plasmonic Fano resonances, thus enabling advantages for high-sensitivity optical sensing and optical switches. Here, we investigate the plasmonic sensing and switches enriched by tailorable multiple Fano resonances that undergo in-plane mirror symmetry or asymmetry in a hybrid rotational misalignment metasurface, which consists of periodic metallic arrays with concentric C-shaped- and circular-ring-aperture unit cells. We found that the plasmonic double Fano resonances can be realized by undergoing mirror symmetry along the X-axis. The plasmonic multiple Fano resonances can be tailored by adjusting the level of the mirror asymmetry along the Z-axis. Moreover, the Fano-resonance-based plasmonic sensing that suffer from mirror symmetry or asymmetry can be implemented by changing the related structural parameters of the unit cells. The passive dual-wavelength plasmonic switches of specific polarization can be achieved within mirror symmetry and asymmetry. These results could entail benefits for metasurface-based devices, which are also used in sensing, beam-splitter, and optical communication systems.
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Rose, Max, Sergey Bobkov, Kartik Ayyer, Ruslan P. Kurta, Dmitry Dzhigaev, Young Yong Kim, Andrew J. Morgan et al. « Single-particle imaging without symmetry constraints at an X-ray free-electron laser ». IUCrJ 5, no 6 (18 septembre 2018) : 727–36. http://dx.doi.org/10.1107/s205225251801120x.

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The analysis of a single-particle imaging (SPI) experiment performed at the AMO beamline at LCLS as part of the SPI initiative is presented here. A workflow for the three-dimensional virus reconstruction of the PR772 bacteriophage from measured single-particle data is developed. It consists of several well defined steps including single-hit diffraction data classification, refined filtering of the classified data, reconstruction of three-dimensional scattered intensity from the experimental diffraction patterns by orientation determination and a final three-dimensional reconstruction of the virus electron density without symmetry constraints. The analysis developed here revealed and quantified nanoscale features of the PR772 virus measured in this experiment, with the obtained resolution better than 10 nm, with a clear indication that the structure was compressed in one direction and, as such, deviates from ideal icosahedral symmetry.
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Yager, Kevin. « Grazing-Transmission Scattering for Measuring Nano-structured Thin Films ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C876. http://dx.doi.org/10.1107/s2053273314091232.

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We describe a new scattering geometry which can be used to quantify three-dimensional nanoscale order in thin films: Grazing-Transmission Small-Angle X-ray Scattering (GTSAXS). This technique collects sub-horizon scattering which exits from the edge of the sample, and does not suffer from the large refraction-distortions and multiple-scattering terms that complicate GISAXS data analysis. We also present a new modelling formalism applicable to superlattices of nano-objects, where lattice symmetry and nano-object size/shape can be arbitrarily defined.
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PARK, CHANG-SOO. « QUANTUM-CLASSICAL CROSSOVER OF THE ESCAPE RATE IN THE NANO-FERROMAGNET WITH COMPLEX CRYSTAL SYMMETRY ». Modern Physics Letters B 15, no 27 (20 novembre 2001) : 1237–47. http://dx.doi.org/10.1142/s0217984901003111.

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We investigate the quantum-classical crossover of the escape rate in the nanoscale ferromagnetic particle with complex crystal symmetries placed in an external field along the hard anisotropy axis. We use the periodic instanton technique based on the spin coherent state representation and the condition of the first-order crossover to determine the type of crossover. In the high field limit of ∊(=1-Hc/H)→0 the crossover is found to be second-order. We also calculate the crossover temperature with leading order behavior of T0~∊1/2.
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