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AbstractAbstract
[en] Highlights: • Interfacial water forms cubic-ice crystallites with a {1 1 0}-preferred orientation. • Four stages of ultrafast structural dynamics of interfacial water are presented. • A nonequilibrium isotropic phase transformation of interfacial ice is identified. • Cooperativity of a hydrogen-bonded network inhibits sublimation during large motions. Using time-averaged and ultrafast electron diffraction, structures and ultrafast dynamics of interfacial water assemblies on smooth hydrophobic surfaces are reported. The lack of hydrophilic interaction and topographical template effect from the support surface leads to the formation of small, mostly randomly-oriented, ice crystallites with the cubic structure. Dynamically, following the substrate photoexcitation, interfacial water assemblies undergo four stages of changes—ultrafast melting, nonequilibrium isotropic phase transformation, annealing, and restructuring—which are closely correlated with the substrate dynamics. The connectivity and cooperative nature of the hydrogen-bonded network is considered crucial for water assemblies to withstand large structural motions without sublimation on ultrashort times.
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S0009261417300921; Available from http://dx.doi.org/10.1016/j.cplett.2017.01.069; Copyright (c) 2017 Elsevier B.V. All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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AbstractAbstract
[en] Steps presence on vicinal surfaces changes the low energy electron difraction (LEED) pattern: a system of regulary spaced steps is causing some spots to be splitted. Using a high voltage LEED apparatus allows an easy explanation of the patterns: the spot position does not depend about energy and so some cristallographic parameters can be easily measured
[fr]
La presence de marches sur les surfaces vicinales change le diagramme de diffraction des electrons lents (LEED). Un systeme de marches espacees regulierement entraine un dedoublement de certains spots de diffraction. Si on utilise un dispositif LEED a haut voltage, on peut expliquer plus facilement les diagrammes: la position du spot ne depend plus de l'energie et les parametres cristallographiques peuvent etre mesures facilementOriginal Title
Application du diffracteur d'electrons lents a objectif a l'etude des faces vicinales
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Source
19. Annual meeting of the French Electron Microscopy Society; Lyon-Villeurbanne, France; 21 - 23 May 1979
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Journal Article
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Conference
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Journal de Microscopie et de Spectroscopie Electroniques; ISSN 0395-9279;
; v. 4(4); p. 451-457

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AbstractAbstract
[en] The basic ideas and possibilities of application of Low Energy Electron Diffraction (L.E.E.D.) are briefly reviewed. The geometry of the diffraction pattern is due to conservation rules together with the periodicity of the crystal surface. The intensity of the diffracted beams is governed by the electron-solid interaction and the multiple scattering effects. The muffin-tin model allows us to split the problem into four parts: scattering by ion-cores; propagation in a constant potential medium, accounting for the many body interactions of the electron with the electron gas; scattering by the surface potential barrier; self-consistent calculation of the effective wave fields. Possibilities of application are large. L.E.E.D. is a powerful method for surface characterization, sensitive to long range order. It is a necessary complement to the methods suited for the chemical determination of the atoms on a surface, such as Auger electron spectroscopy of X-ray photoelectron spectroscopy. Applications to surface crystallography are still limited to simple superstructures. The analyses are far too much expensive. A suitable choice of the experimental basis should probably reduce their cost to a level manageable for many laboratories
[fr]
Les fondements et les possibilites d'application de la Diffraction des Electrons Lents (D.E.L.) sont passes rapidement en revue. La geometrie de la figure de diffraction resulte de lois de conservation et de la periodicite de la surface. L'intensite des faisceaux diffractes resulte de l'interaction electron-solide et des effets de diffraction multiple. Grace au modele muffin-tin, on peut separer le probleme en plusieurs parties: diffusion par le potentiel des coeurs ioniques; propagation dans un milieu a potentiel constant effectif, traduisant les interactions a N corps dans le gaz d'electron; traitement de la barriere de potentiel en surface; construction du champ d'onde effectif pour le calcul des intensites. Les possibilites d'application sont nombreuses: la D.E.L. est un puissant outil de caracterisation, sensible a l'ordre a grande distance, complement necessaire aux methodes d'identification chimique des atomes de surface. En cristallographie des surfaces, les possibilites sont encore limitees aux surstructures simples. Le cout des analyses est probablement tres surfait. Un bon choix de la base experimentale devrait le rendre accessible a la plupart des laboratoiresOriginal Title
Diffraction des electrons lents
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Colloquium on recent methods for solids analysis; Dijon, France; 30 Jun 1975
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Journal Article
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Conference
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Revue de Physique Appliquee; v. 11(1); p. 1-11
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[en] Being an independent method of structure analysis, electron diffraction provides original data which are essential contributions to all the fields where this method is used. An important place of electron diffraction among other structural methods is illustrated by the results of the studies once started on clay minerals and continued on the objects extremely important for structural mineralogy, which stimulated the development of a new field - modular crystallography
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Translated from Kristallografiya, ISSN 0023-4761, 46, 614-619 (No. 4, 2001); (c) 2001 MAIK ''Nauka / Interperiodica''.; Country of input: International Atomic Energy Agency (IAEA)
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Kobe, D.H.; Aguilera-Navarro, V.C.; Ricotta, R.M.
Instituto de Fisica Teorica (IFT), Sao Paulo, SP (Brazil)1991
Instituto de Fisica Teorica (IFT), Sao Paulo, SP (Brazil)1991
AbstractAbstract
[en] The electron diffraction pattern for two-slits with magnetic flux confined to an inaccessible region between them is calculated. The Aharonov-Bohm effect gives a diffraction pattern which is asymmetric but with a symmetric envelope. In general, both expected displacement and kinetic momentum of the electron are nonzero as a consequence of the asymmetry. Nevertheless Ehrenfest's theorems and the conservation of momentum are satisfied. (author)
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Jun 1991; 13 p
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Report
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[en] Phase transformations in TlIn1-xSnxS2 films with a thickness of 30 nm were investigated by the electron diffraction method. It has been established that the interaction of atoms of the ternary compound with Sn atoms implanted as an impurity leads to the formation of substitution solid solutions with a superstructure in the composition range of 0.02 ≤ x ≤0.09 mol. %. A superstructure with a tetragonal system, which has threefold parameters with respect to the initial phase, has been revealed.
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2 figs.; 8 refs.
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Journal of Radiation Researches; ISSN 2312-3001;
; v. 5(2); p. 67-70

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AbstractAbstract
No abstract available
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Vide; v. 28(167); p. 159-169
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[en] By the materials of the lecture delivered in the School on Electron Crystallography, Erice, Sicily, 1997 and published in Proceedings of NATO Advanced Study Institute on Electron Crystallography, Erice, Sicily, 1997, Series E, vol. 347, p. 1
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Translated from Kristallografiya, ISSN 0023-4761, 46, 982-990 (No. 6, 2001); (c) 2001 MAIK ''Nauka / Interperiodica''.; Country of input: International Atomic Energy Agency (IAEA)
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AbstractAbstract
[en] A wave approach of electron scattering by crystals is presented. A notion of coherence between the Bloch waves components is introduced. The first results, in agreement with the existing theories, permit the interpretation of the contrast of diffraction patterns
[fr]
On propose une approche ondulatoire de la diffusion des electrons par les cristaux. Pour cela on introduit une notion de coherence entre les composantes des ondes de Bloch. Les premiers resultats, en accord avec les theories existantes, permettent d'interpreter les contrastes obtenus en diffraction electroniqueOriginal Title
Diffusion dynamique coherente et incoherente, application a l'etude des diagrammes de lignes
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Journal Article
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Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences. Serie B; v. 280(14); p. 443-446
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[en] A Bloch-wave analysis is made of the problem of uncoupling surface superlattice reflections from fundamental reflections in transmission electron diffraction (TED) analysis of reconstructed surfaces. This uncoupling problem is proved to be of crucial importance in determining the structure of reconstructed surfaces, for example the Si(111) 7x7 surface. It is found that a complete uncoupling, weak coupling and sometimes strong coupling between the bulk scattering and surface superlattice scattering are all possible depending on the diffraction conditions. For a kinematical analysis of reconstructed surfaces to be valid, a weak coupling or a complete uncoupling condition must be realized. General rules for choosing the appropriate diffraction conditions are given. (orig.)
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Journal Article
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Acta Crystallographica. Section A: Foundations of Crystallography; ISSN 0108-7673;
; CODEN ACACE; v. 47(2); p. 101-109

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