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Crystallography, Cristallographie cristallogenèse, Geology, Géologie, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Equations d'état, équilibres de phases et transformations de phases, Equations of state, phase equilibria, and phase transitions, Solubilité, ségrégation, mélanges et séparation de phases, Solubility, segregation, and mixing; phase separation, Propriétés de transport (non électroniques), Transport properties of condensed matter (nonelectronic), Diffusion dans les solides, Diffusion in solids, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Méthodes de croissance cristalline; physique de la croissance cristalline, Methods of crystal growth; physics of crystal growth, Croissance en phase fondue; fusion de zone et purification de zone, Growth from melts; zone melting and refining, Diagrammes de phases et microstructures développées par solidification et par transformations de phases solide-solide, Phase diagrams and microstructures developed by solidification and solid-solid phase transformations, Solidification, Contrainte cisaillement, Shear stress, Tensión cizallamiento, Convection naturelle, Natural convection, Croissance cristalline en phase fondue, Crystal growth from melts, Diffusion(transport), Diffusion, Donnée expérimentale, Experimental data, Ecoulement fluide, Fluid flow, Etude théorique, Theoretical study, Interface, Interfaces, Loi échelle, Scaling laws, Modélisation, Modelling, Méthode phase fondue, Growth from melt, Método fase fundida, Simulation numérique, Digital simulation, Simulation ordinateur, Computerized simulation, Solidification dirigée, Directional solidification, Ségrégation, Segregation, Transfert chaleur, Heat transfer, Transfert masse, Mass transfer, 8110F, 8130F, A1. Convection, A1. Directional solidification, A1. Segregation, and A2. Growth from melt

The effect of natural convection on solute segregation in the horizontal Bridgman configuration is studied. The objective is to check whether a single non-dimensional number, based on the fluid flow induced interface shear stress, is able to capture the physics of the mass transport phenomena. A number of heat and mass transfer numerical simulations are carried out in the laminar convection regime, and the segregation results are found to be in good agreement with the predictions of the scaling analysis. At the higher convective levels relevant for the comparison with existing experimental data, a direct computation of the segregation phenomena is not possible, but numerical simulations accounting for turbulence modeling can provide the interface shear stress. With this procedure, a good agreement between the experimentally measured segregation and the predictions of the scaling analysis is again observed, thus validating the choice of the interface shear stress as a key parameter for the segregation studies.

Crystallography, Cristallographie cristallogenèse, Geology, Géologie, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés de transport (non électroniques), Transport properties of condensed matter (nonelectronic), Diffusion dans les solides, Diffusion in solids, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Méthodes de croissance cristalline; physique de la croissance cristalline, Methods of crystal growth; physics of crystal growth, Théorie et modèles de la croissance cristalline; physique de la croissance cristalline, morphologie cristalline et orientation cristalline, Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation, Méthodes de dépôt de films et de revêtements; croissance de films et épitaxie, Methods of deposition of films and coatings; film growth and epitaxy, Dépôt chimique en phase vapeur (incluant le cvd activé par plasma, mocvd, etc.), Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.), Epitaxie en phase vapeur; croissance en phase vapeur, Vapor phase epitaxy; growth from vapor phase, Basse pression, Low pressure, Composé III-V, III-V compound, Compuesto III-V, Couche contrainte, Strained layer, Capa forzada, Diffusion(transport), Diffusion, Dépendance température, Temperature dependence, Désorption, Desorption, Epitaxie phase vapeur, VPE, Etude théorique, Theoretical study, Indium, Mécanisme croissance, Growth mechanism, Mecanismo crecimiento, Méthode MOCVD, MOCVD, Méthode MOVPE, MOVPE method, Método MOVPE, Nitrure, Nitrides, Semiconducteur III-V, III-V semiconductors, Taux croissance, Growth rate, 8110A, 8115G, 8115K, GaN, InGaN, Substrat GaN, Substrat saphir, Growth models, Metalorganic vapor phase epitaxy, and Semiconducting III-V materials

InGaN strained bulk layers were grown by low-pressure metalorganic chemical vapor deposition on c-plane GaN/sapphire templates. Two growth regimes, mass-transport limited regime and indium desorption regime, were examined for InGaN growth. In the indium desorption regime, more indium source must be fed to keep a constant indium content. In the indium desorption regime, we found an abnormally enhanced GaN growth rate, which was proved to be related to the indium desorption and dependent on the growth temperature and the indium source flow. Due to the enhanced growth rate, the optical quality of In0.16Ga0.84N layers degraded significantly.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Analyse contrainte, Stress analysis, Análisis tensión, Etude théorique, Theoretical study, Estudio teórico, Matériau aiguilleté, Needled material, Material cosado, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Modélisation, Modeling, Modelización, Méthode élément fini, Finite element method, Método elemento finito, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété travers court, Through thickness property, Propiedad corta travesía, Résistance compression, Compressive strength, Resistencia compresión, Résistance traction, Tensile strength, Resistencia tracción, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, Tissu textile, Woven material, Tela textil, A. Fabrics/textiles, A. Polymer-matrix composites (PMCs), C. Analysis, and D. Mechanical testing

A multiscale approach is used to predict transverse tensile and transverse compressive strength of unidirectional non-crimp fabric (NCF) composites. Numerical analysis on fibre/matrix scale is performed to obtain the transverse strength of the fibre bundle to be further used in an analytical mesoscale model to predict the strength of the unidirectional NCF composite. Design of unidirectional layer composites with the same fibres, interface, matrix and volume fractions as in the bundle is suggested as an alternative method for bundle strength determination. Good agreement of both methods for bundle transverse strength determination is demonstrated. The simple analytical model used on mesoscale gives accurate predictions of the tensile transverse strength whereas the compressive strength is underestimated. The necessity of including bundle waviness in models when bidirectional NCF composites are analysed is demonstrated by FEM stress analysis and by experimental data showing differences in transverse cracking pattern due to bundle waviness.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Surfaces et interfaces; couches minces et trichites (structure et propriétés non électroniques), Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties), Structure et morphologie de couches minces, Thin film structure and morphology, Structure et morphologie; épaisseur, Structure and morphology; thickness, Propriétés physiques non électroniques de couches minces, Physical properties of thin films, nonelectronic, Propriétés mécaniques et acoustiques, Mechanical and acoustical properties, Acier inoxydable 316L, Stainless steel-316L, Adhérence, Adhesion, Alliage base nickel, Nickel base alloys, Article synthèse, Reviews, Couche mince amorphe, Amorphous thin film, Capa fina amorfa, Couche mince métallique, Metallic thin films, Couche mince, Thin films, Durée vie, Lifetime, Déformation, Deformation, Epaisseur couche, Layer thickness, Espesor capa, Etude expérimentale, Experimental study, Etude théorique, Theoretical study, Flexion, Bending, Instabilité, Instability, Matériau revêtu, Coated material, Material revestido, Méthode élément fini, Finite element method, Propriété mécanique, Mechanical properties, Revêtement, Coatings, Résistance corrosion, Corrosion resistance, Simulation numérique, Digital simulation, Tribologie, Tribology, Verre métallique, Metallic glasses, 4335N, 6855J, 6860B, Substrat verre, Coating, Fatigue lifetime, Fatigue-crack initiation, Finite-element model, and Thin-film metallic glass (TFMG)

Amorphous metallic films, a thin form of metallic glasses, have been attracting more and more attentions in the last two decades, due to their unique properties, compared with the conventional crystalline films, such as high strength, high toughness, large elastic limits, and high-corrosion resistance. However, the deformation mechanisms of thin-film metallic glasses (TFMGs) are still far from in-depth understanding, although some of their properties and characteristics are not as good as metallic or ceramic films. This paper will focus on reviewing and discussing the fatigue behavior of structural-material substrates coated with TFMGs. The substrates include 316L stainless steel, Al-based, Ni-based, Zr-based, and Ti-based alloys. The results show that the four-point-bending fatigue life of the substrates is greatly improved by Zr- and Cu-based TFMGs, while Fe-based TFMG, TiN, and pure-Cu films are not so beneficial in extending the fatigue life of 316L stainless steel. In comparison, the tension-tension fatigue lifetime and endurance limit of 316L stainless steel cannot be improved by the Zr- and Cu-based TFMGs. However, the TFMGs annealed at a temperature within the supercooled liquid region (ΔT) can further improve the fatigue behavior, compared to as-deposited TFMGs. The fatigue mechanisms of crystalline and bulk metallic glass (BMG) materials, together with TFMGs, are reviewed in the present work. Crystals and BMGs present 3-stage and 4-stage fatigue-deformation mechanisms, respectively. The fatigue life of medium-strength structural materials tends to be significantly improved by TFMGs. A synergistic experimental/theoretical study has shown the micro-mechanisms of the fatigue behavior of TFMGs adhered to substrates, as well as film-adhesion and thickness effects on fatigue behavior of the substrate. Furthermore, shear-band initiation and propagation under bending deformation are investigated using the Rudnicki-Rice instability theory and the free-volume models employing finite-element simulations.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Epoxyde résine, Epoxy resin, Epóxido resina, Etude théorique, Theoretical study, Estudio teórico, Fibre minérale, Mineral fiber, Fibra inorgánica, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Mode rupture, Fracture mode, Modo ruptura, Modèle 3 dimensions, Three dimensional model, Modelo 3 dimensiones, Modèle statistique, Statistical model, Modelo estadístico, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Méthode élément fini, Finite element method, Método elemento finito, Propagation fissure, Crack propagation, Propagación fisura, Propagation oblique, Oblique propagation, Propagación oblicua, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété traction, Tensile property, Propiedad tracción, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, Vérification expérimentale, Experimental test, Verificación experimental, Matériau fibre multidirectionnelle, Stratifié croisé, A. Polymer-matrix composites, B. Defects, C. Damage mechanics, and C. Statistical properties/methods

A previously developed statistical model for transverse cracking in cross ply laminates is extended to oblique cracking in multidirectional laminates. The oblique cracks are assumed to form in a ply when the local in-plane tensile stress normal to fibers exceeds the transverse strength of the ply. This strength is assumed to have a statistical distribution given by a two-parameter Weibull function. The model is applied to a glass-epoxy [0/602/0/-602]5 laminate in which cracking evolution of the four -60° plies in the middle of the laminate is examined. The local stress field in the cracked -60° plies is calculated by a three-dimensional finite element method based on a unit cell construction developed by Li et al. [1]. The measured crack density is found to agree well with that calculated by the statistical model.

Crystallography, Cristallographie cristallogenèse, Geology, Géologie, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Structure des liquides et des solides; cristallographie, Structure of solids and liquids; crystallography, Etat cristallin (incluant les mouvements moléculaires dans les solides), Crystalline state (including molecular motions in solids), Théorie de la structure cristalline, symétrie cristalline; calculs et modélisation, Theory of crystal structure, crystal symmetry; calculations and modeling, Structure de solides cristallins particuliers, Structure of specific crystalline solids, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Effets de hautes pressions et des ondes de choc dans les solides et les liquides, High-pressure and shock-wave effects in solids and liquids, Diagramme poudre, Powder pattern, Diagrama polvo, Effet haute pression, High-pressure effects, Espace phase, Phase space, Etude cas, Case study, Estudio caso, Etude théorique, Theoretical study, Groupe espace, Space groups, Haute pression, High pressure, Modélisation, Modelling, Méthode Rietveld, Rietveld method, Método Rietveld, Ordre 2, Second order, Orden 2, Propriété symétrie, Symmetry property, Propiedad simetría, Précipité, Precipitates, Relation empirique, Empirical relation, Relación empírica, Structure cristalline, Crystal structure, Symétrie cristalline, Crystal symmetry, Transition phase, Phase transitions, Transición fase, 6150A, LaFeO3, high pressure, parametric rietveld refinement, phase transition, and rotational symmetry modes

Parametric Rietveld refinement is a powerful technique to apply directly physical or empirical equations to the refinement of in situ powder diffraction data. In order to investigate the possibilities and limitations of parametric Rietveld refinements for high pressure data four competitive crystallographic approaches were used to carry out a full structural investigation of the orthoferrite LaFeO3 (Pbnm at ambient conditions) under high pressure up to 47 GPa. Approach A with traditional Rietveld refinement using atomic coordinates, Approach B where the Rietveld refinement was done by using the rigid body method, Approach C where symmetry modes were used and Approach D where the newly developed method of the rotational symmetry mode description for a rigid body was used. For all approaches sequential as well as parametric refinements were carried out, confirming a second order phase transition of LaFeO3 to a higher symmetric phase (space group Ibmm) at around 21.1 GPa and an isostructural first order phase transition at around 38 GPa. Limitations due to non-hydrostatic conditions as well as the possibilities of a direct modeling of phase transitions with parametric Rietveld refinement are discussed in detail.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Surfaces et interfaces; couches minces et trichites (structure et propriétés non électroniques), Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties), Propriétés physiques non électroniques de couches minces, Physical properties of thin films, nonelectronic, Propriétés mécaniques et acoustiques, Mechanical and acoustical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Méthodes de dépôt de films et de revêtements; croissance de films et épitaxie, Methods of deposition of films and coatings; film growth and epitaxy, Depôt par pulvérisation cathodique, Deposition by sputtering, Anisotropie, Anisotropy, Constante élasticité, Elastic constants, Couche mince amorphe, Amorphous thin film, Capa fina amorfa, Couche mince métallique, Metallic thin films, Couche mince, Thin films, Donnée expérimentale, Experimental data, Dureté, Hardness, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Déformation, Deformation, Dépôt pulvérisation, Sputter deposition, Effet dimensionnel, Size effect, Empreinte dureté, Hardness indentation, Indentación dureza, Essai dureté, Hardness testing, Etude théorique, Theoretical study, Fonction distribution radiale, Radial distribution function, Función distribución radial, Indentation, Module Young, Young modulus, Méthode dynamique moléculaire, Molecular dynamics method, Nanodureté, Nanohardness, Nanodureza, Nanoindentation, Nanoindentacion, Potentiel paire, Pair potentials, Propriété mécanique, Mechanical properties, Rayonnement synchrotron, Synchrotron radiation, Relaxation structurale, Structure relaxation, Relajación estructural, Simulation numérique, Digital simulation, Verre métallique, Metallic glasses, 4335N, 6860B, 8115C, Substrat titane, Metallic glass, and Thin film

In this paper, the (Cu50Zr50)100―xAlx (X = 0, 2, 4, 5, 6, 8, 10, 12, atomic percent) metallic-glass thin films on the titanium crystalline substrate were constructed by using molecular dynamics (MD) to simulate sputter deposition. The deposition simulations adopted a tight-binding potential with consideration of argon working gas from the pair-wise Moliere potential. The as-deposited films were amorphous and used as initial structures for nano-indentation simulations with a right-angle conical indenter tip to obtain their mechanical properties. All simulations were carried out at temperature 300 K to compare with experimental data. The radial distribution function of the film is calculated and compared with synchrotron experimental data. From the nanoindentation simulations, the hardness and Young's modulus of the films were calculated, as well as the pileup index under two different depth-to-thickness ratios. Our MD simulation results are consistent with experimental data. Furthermore, atomic strains were calculated to reveal deformation localization. In addition, elastic constants of the film and associated degrees of elastic anisotropy were studied to correlate structural anisotropy and to reveal structural relaxation. It is found that the deposited and MD-equilibrated films have notable anisotropic elastic constants, and their relaxation can be observed at the MD time scales.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Electrotechnique. Electroenergetique, Electrical engineering. Electrical power engineering, Electroénergétique, Electrical power engineering, Conversion directe et accumulation d'énergie, Direct energy conversion and energy accumulation, Conversion électrochimique: piles et accumulateurs électrochimiques, piles à combustibles, Electrochemical conversion: primary and secondary batteries, fuel cells, Batterie lithium, Lithium battery, Diffusion ion, Ion scattering, Difusión ión, Distribution concentration, Concentration distribution, Distribución concentración, Elasticité linéaire, Linear elasticity, Elasticidad lineal, Endommagement, Damaging, Deterioración, Etude théorique, Theoretical study, Estudio teórico, Exfoliation, Exfoliación, Fibre carbone, Carbon fiber, Fibra carbón, Fibre minérale, Mineral fiber, Fibra inorgánica, Ion lithium, Lithium ion, Litio ión, Matériau électrode, Electrode material, Material electrodo, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Méthode élément fini, Finite element method, Método elemento finito, Propriété mécanique, Mechanical properties, Propiedad mecánica, Simulation numérique, Numerical simulation, Simulación numérica, A. Carbon fiber, and C. Finite element analysis (FEA)

Gradients in lithium ion concentration distribution in carbon fiber are accompanied by non-uniform fiber swelling leading to development of mechanical stresses. During lithium deintercalation these stresses may lead to initiation and growth of radial cracks in the fiber. The subsequent cycle of intercalation may result in arc-shaped cracks deviating from the tip of the radial cracks. These phenomena decrease the mechanical properties of fibers if used in structural batteries and reduce the charging properties of the battery by decreased diffusivity of lithium ions and by exfoliating layers on the fiber surface. The crack propagation and possible damage evolution scenarios are analyzed using linear elastic fracture mechanics. The crack geometry dependent ion concentration distributions and the elastic stress distributions were found using finite element software ANSYS.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Concentration contrainte, Stress concentration, Concentración restringida, Endommagement, Damaging, Deterioración, Epoxyde résine, Epoxy resin, Epóxido resina, Etude théorique, Theoretical study, Estudio teórico, Fibre minérale, Mineral fiber, Fibra inorgánica, Fibre verre, Glass fiber, Fibra vidrio, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Modèle mécanique, Mechanical model, Modelo mecánico, Modélisation, Modeling, Modelización, Mécanique milieu continu, Continuum mechanics, Mecánica medio contínuo, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Orientation fibre, Fiber orientation, Orientación fibra, Plaque perforée, Perforated plate, Placa perforada, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété traction, Tensile property, Propiedad tracción, Rupture fibre, Fibre fracture, Ruptura fibra, Résistance fatigue, Fatigue strength, Resistencia fatiga, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, A. Laminates, B. Fatigue, B. Stress concentrations, and C. Damage mechanics

A model defined at the ply scale to predict the failure of laminated composites for static and fatigue loadings has been proposed. The model describes the loss of strength in the fibre direction for high levels of transverse damage. This phenomenon can be observed in a 0° tube by applying a cyclic torsion loading up to a high level of damage followed by a tensile test. The model includes an original approach based on a Fracture Characteristic Volume (FCV) to predict the fibre failure of laminated structures with stress concentrations. The FCV is a cylinder defined at the ply scale where the average stress is calculated and compared to the maximal strength of the material. The fibre failure model and an application to open hole plates loaded in fatigue are presented in this paper.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Mécanique de la rupture (fissure, fatigue, endommagement...), Fracture mechanics (crack, fatigue, damage...), Sciences appliquees, Applied sciences, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Stratifiés, Laminates, Contrainte biaxiale, Biaxial stress, Tensión biaxial, Critère rupture, Fracture criterion, Criterio ruptura, Epoxyde résine, Epoxy resin, Epóxido resina, Etude théorique, Theoretical study, Estudio teórico, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Micromécanique, Micromechanics, Mode rupture, Fracture mode, Modo ruptura, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Méthode élément frontière, Boundary element method, Método elemento frontera, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété traction, Tensile property, Propiedad tracción, Rupture fibre, Fibre fracture, Ruptura fibra, Résistance compression, Compressive strength, Resistencia compresión, Simulation numérique, Numerical simulation, Simulación numérica, Stratifié, Laminate, Estratificado, B. Transverse cracking, Biaxial loads, C. Micro-mechanics, and C. Numerical analysis

At present, the progress in the failure criteria of unidirectional reinforced laminates requires the study of the evolution of the mechanisms of damage at micromechanical level. The objective of this paper is the study of the influence (at micromechanical scale) of a secondary transverse load (tension or compression), perpendicular to the transverse compression nominally responsible for the failure, on the inter-fibre failure under compression. The Boundary Elements Method and Interfacial Fracture Mechanics concepts are employed. It is shown that a secondary tension accelerates the generation of failure whereas a secondary compression inhibits it.

Crystallography, Cristallographie cristallogenèse, Geology, Géologie, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Etats électroniques, Electron states, Méthodes de calcul de structure électronique, Methods of electronic structure calculations, Structure électronique et propriétés électriques des surfaces, interfaces, couches minces et structures de basse dimensionnalité, Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures, Phénomènes de transport électronique dans les couches minces et les structures de basse dimensionnalité, Electronic transport phenomena in thin films and low-dimensional structures, Article synthèse, Reviews, Constante élasticité, Elastic constants, Dynamique réticulaire, Lattice dynamics, Etude théorique, Theoretical study, Haute pression, High pressure, Interaction échange, Exchange interactions, Méthode fonctionnelle densité, Density functional method, Propriété physique, Physical properties, Transition phase, Phase transitions, Transición fase, 7115M, density functional theory, elastic coefficients, exchange-correlation functional, high pressure, lattice dynamics, and phase transitions

Density functional theory based calculations are commonly employed to complement experimental high pressure research. Here, a brief overview of the underlying theory and available codes is provided, followed by some applications. The influence of the choice of the exchange-correlation functional on predicted structural parameters and physical properties is discussed.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Surfaces et interfaces; couches minces et trichites (structure et propriétés non électroniques), Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties), Propriétés physiques non électroniques de couches minces, Physical properties of thin films, nonelectronic, Propriétés mécaniques et acoustiques, Mechanical and acoustical properties, Analyse dimensionnelle, Dimensional analysis, Análisis dimensional, Charge uniaxiale, Uniaxial load, Carga uniaxial, Confinement, Couche mince, Thin films, Couche multimoléculaire, Multilayer, Capa multimolecular, Déformation plastique, Plastic deformation, Ecoulement plastique, Plastic flow, Effet contrainte, Stress effects, Etude théorique, Theoretical study, Interface, Interfaces, Modélisation, Modelling, Multicouche, Multilayers, Méthode élément fini, Finite element method, Propriété mécanique, Mechanical properties, Verre métallique, Metallic glasses, 4335N, 6860B, Substrat verre, Finite element analysis, Metallic glass, Shear band, and Thin film

Localized plastic deformation known as shear banding is a prominent feature in metallic glasses. In this study we perform parametric three-dimensional finite element analyses, using primarily a thin layer of metallic glass on top of a cylindrical base, to study how physical constraint can affect this localized form of deformation and the corresponding macroscopic stress―strain response. Random perturbation points are added to the metallic glass model to facilitate the formation of shear bands. The modeling result suggests that the mechanical behavior of metallic glasses can be significantly influenced by the geometrical confinement. Under nominally uniaxial compressive loading, a lower thickness-to-diameter ratio results in higher plastic flow stresses. Shear bands tend to concentrate in regions away from the interface with the base material. The findings provide a mechanistic rationale for experimental observations based on the micropillar compression test. The deformation pattern in a multilayered metallic glass structure is also examined.

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Batiment. Travaux publics, Buildings. Public works, Calcul des constructions. Sollicitations, Structural analysis. Stresses, Résistance des matériaux (élasticité, plasticité, flambage, etc.), Strength of materials (elasticity, plasticity, buckling, etc.), Matériaux, Materials, Bétons. Mortiers. Coulis, Concretes. Mortars. Grouts, Généralités (composition, classification, performances, normes, brevets, etc.), General (composition, classification, performance, standards, patents, etc.), Béton de ciment, Cement concrete, Hormigón cemento, Etude théorique, Theoretical study, Estudio teórico, Matériau composite, Composite material, Material compuesto, Micromécanique, Micromechanics, Module Young, Young modulus, Módulo Young, Modèle mécanique, Mechanical model, Modelo mecánico, Modélisation, Modeling, Modelización, Mécanique rupture, Fracture mechanics, Mecánica ruptura, Propriété mécanique, Mechanical properties, Propiedad mecánica, Propriété non linéaire, Non linear properties, Propiedad no lineal, Relation contrainte déformation, Stress strain relation, Relación tensión deformación, Résistance compression, Compressive strength, Resistencia compresión, Simulation numérique, Numerical simulation, Simulación numérica, B. Elasticity, B. Strength, B. Stress concentrations, and C. Micro-mechanics

In this contribution, a four-phase micromechanical model is proposed in order to simulate the non-linear instantaneous pre-peak response of cement concrete subjected to monotonically increasing loads. The non-linear behavior is attributed to the creation of cracks in the cement paste of the concrete; the effect of the cracks is taken into account by introducing equivalent voids in the cement paste. The concrete material is modeled as a four-phase composite with three different types of heterogeneities: gravel, sand and voids, embedded in a cement pure paste matrix. The composite homogenization is realized with the Mori-Tanaka method and the overall non-linear response of the concrete is determined by a secant approach. The proposed micromechanical model is able to capture peculiar aspects of the concrete stress-strain curve of uniaxial compression: in most concrete materials, a higher compressive strength is associated with a higher initial tangent Young's modulus. Further analogies between the theoretical curves of the proposed method and the experimental curves are shown.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Surfaces et interfaces; couches minces et trichites (structure et propriétés non électroniques), Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties), Structure et morphologie de couches minces, Thin film structure and morphology, Structure et morphologie; épaisseur, Structure and morphology; thickness, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Etats électroniques, Electron states, Méthodes de calcul de structure électronique, Methods of electronic structure calculations, Structure électronique et propriétés électriques des surfaces, interfaces, couches minces et structures de basse dimensionnalité, Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures, Phénomènes de transport électronique dans les couches minces et les structures de basse dimensionnalité, Electronic transport phenomena in thin films and low-dimensional structures, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Matériaux particuliers, Specific materials, Autres semiconducteurs, Other semiconductors, Bicouche, Bilayers, Composé III-V, III-V compound, Compuesto III-V, Couche intermédiaire, Interlayers, Dislocation, Dislocations, Epaisseur couche, Layer thickness, Espesor capa, Etat métastable, Metastable states, Etude théorique, Theoretical study, Mécanique milieu continu, Continuum mechanics, Méthode fonctionnelle densité, Density functional method, Méthode élément fini, Finite element method, Réseau cubique, Cubic lattices, Semiconducteur III-V, III-V semiconductors, Superréseau, Superlattices, Valeur critique, Critical value, Valor crítico, 6855J, 7115M, 8105E, Substrat Aluminium, Substrat MgO, Ti1-xAlxN, Coherency, Density Functional Theory, Finite Element Analysis, and Superlattice

We combine the continuum mechanics with first principle calculations to study and predict the critical thickness up to which the metastable cubic (c) AlN phase is energetically preferred to the stable wurtzite (w) variant in AlN/Ti1-xAlxN bi-layer systems. The results show that c-AlN is favored with increasing Al content of the Ti1-xAlxN layer on both Al and MgO substrates. Dislocations in the AlN/Ti1-xAlxN bi-layer system relax the bi-axial strain, and thus reduce the critical thickness up to which the AlN layers can be stabilized in their metastable cubic structure. Finally, the varying interlayer thickness of Ti1-xAlxN in the AlN/Ti1-xAlxN bi-layer system in free standing configuration (without substrate) and on MgO substrate showed that c-AlN can be stabilized up to 17 nm with increasing the Ti1-xAlxN layer thickness above 100 nm.

Crystallography, Cristallographie cristallogenèse, Chemical industry parachemical industry, Industrie chimique et parachimique, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Diagrammes de phases et microstructures développées par solidification et par transformations de phases solide-solide, Phase diagrams and microstructures developed by solidification and solid-solid phase transformations, Transformations de phases solide-solide à composition constante: polymorphes, massives, ordre-désordre, Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder, Traitement des matériaux et son effet sur la microstructure et les propriétés, Treatment of materials and its effects on microstructure and properties, Autres traitements thermiques et thermomécaniques, Other heat and thermomechanical treatments, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Transformation de matériaux métalliques, Production techniques, Traitements thermiques, Heat treatment, Traitements thermomécaniques, Thermomechanical treatment, Acier faiblement allié, Low alloy steels, Acier haute résistance, High-strength steels, Affinement grain, Grain refinement, Charge dynamique, Dynamic loads, Effet contrainte, Stress effects, Etude théorique, Theoretical study, Laminage à chaud, Hot rolling, Modélisation, Modelling, Méthode échelle multiple, Multiscale method, Método escala múltiple, Onde contrainte, Stress wave, Onda tensión, Structure grain fin, Fine grain structure, Estructura grano fino, Feinkorngefuege, Traitement matériau, Material processing, Tratamiento material, Traitement thermomécanique, Thermomechanical treatments, Transformation phase, Phase transformations, 8130H, 8140G, High strength steel, Modeling, Rolling, and Ultrafine-grained steel

The aim of the work is development of industry guidance concerning production of ultrafine-grained (UFG) High Strength Low Alloy (HSLA) steels using strain-induced dynamic phase transformations during advanced thermomechanical processing. In the first part of the work, the effect of processing parameters on the grain refinement was studied. Based on the obtained results, a multiscale computer model was developed in the second part of the work that was subsequently used to predict the mechanical response of studied structures. As an overall outcome, a process window was established for the production of UFG steels that can be adopted in existing hot rolling mills.

Crystallography, Cristallographie cristallogenèse, Electronics, Electronique, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Generalites, General, Instruments, appareillage, composants et techniques communs à plusieurs branches de la physique et de l'astronomie, Instruments, apparatus, components and techniques common to several branches of physics and astronomy, Techniques, équipements et instruments mécaniques, Mechanical instruments, equipment and techniques, Instrumentation pour déformation, force et couple, Instruments for strain, force and torque, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Contrôle, Analysing. Testing. Standards, Analyse des contraintes, Stress analysis, Analyse contrainte, Stress analysis, Análisis tensión, Spannungsanalyse, Analyse thermique, Thermal analysis, Análisis térmico, Thermische Analyse, Circuit intégré, Integrated circuit, Circuito integrado, Integrierte Schaltung, Coefficient dilatation thermique, Thermal expansion coefficient, Coeficiente dilatación térmica, Thermischer Ausdehnungskoeffizient, Contrainte thermique, Thermal stress, Tensión térmica, Waermespannung, Effet contrainte, Stress effects, Etude théorique, Theoretical study, Estudio teórico, Theoretische Untersuchung, Microstructure, Microestructura, Mikrogefuege, Modélisation, Modeling, Modelización, Méthode paramétrique, Parametric method, Método paramétrico, Méthode statistique, Statistical method, Método estadístico, Méthode élément fini, Finite element method, Método elemento finito, Finite Element Methode, Trou interconnexion, Via hole, Agujero interconexión, 0710P, IC integration, TSV interposer, finite-element analysis, modeling, and thermal stress

The thermal stress of typical integrated circuit (IC) integration with the interposer of through silicon via (TSV) was investigated in this study. To overcome the huge computational costs due to meshing the large amount of TSVs' microstructures, a simplified method, i.e. the complement sector model, was proposed and verified by the symmetric 1/8th full model. Using the sector model, the parametric studies were carried out to reveal the critical locations of TSV and the crucial parameters. Furthermore, statistical methods were invoked to clarify the impact of the major parameters, such as the modulus and coefficient of thermal expansion of underfill materials, the pitch and diameter of TSV, etc. Upon the analysis results, the design of minimized stress in TSV for the IC integration with TSV interposer was achieved.

Crystallography, Cristallographie cristallogenèse, Chemical industry parachemical industry, Industrie chimique et parachimique, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Structure des liquides et des solides; cristallographie, Structure of solids and liquids; crystallography, Structure de solides cristallins particuliers, Structure of specific crystalline solids, Défauts et impuretés dans les cristaux; microstructure, Defects and impurities in crystals; microstructure, Défauts d'empilement et autres défauts plans ou étendus, Stacking faults and other planar or extended defects, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Traitement des matériaux et son effet sur la microstructure et les propriétés, Treatment of materials and its effects on microstructure and properties, Elasticité et anélasticité, Elasticity and anelasticity, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Elasticité. Plasticité, Elasticity. Plasticity, Asymétrie, Asymmetry, Asimetría, Asymmetrie, Compression uniaxiale, Uniaxial compression, Compresión uniaxial, Contrainte compression, Compressive stress, Tensión compresión, Druckspannung, Dislocation imparfaite, Partial dislocation, Dislocación imperfecta, Teilversetzung, Défaut empilement, Stacking fault, Defecto apilado, Stapelfehler, Dépendance température, Temperature dependence, Effet contrainte, Stress effects, Effet température, Temperature effect, Efecto temperatura, Temperatureinfluss, Essai traction compression, Tension compression fatigue test, Ensayo tracción compresión, Zug Druck Dauerversuch, Etude théorique, Theoretical study, Estudio teórico, Theoretische Untersuchung, Germination dislocation, Dislocation nucleation, Germinación dílocación, Versetzungskeimbildung, Germination homogène, Homogeneous nucleation, Germinación homogénea, Homogene Keimbildung, Mode empilement, Stacking sequence, Modo apilamiento, Monocristal, Single crystal, Einkristall, Méthode dynamique moléculaire, Molecular dynamics method, Método dinámico molecular, Plan glissement, Slip plane, Plano deslizamienta, Gleitebene, Propriété traction, Tensile property, Propiedad tracción, Zugeigenschaft, Réseau cubique face centrée, FCC lattices, Structure atomique, Atomic structure, Estructura atómica, Atomstruktur, Structure cristalline, Crystalline structure, Estructura cristalina, Kristallstruktur, Traction uniaxiale, Uniaxial tension stress, Tracción uniaxial, 6172N, 8140J, Ni3Al, Dislocation nucleation stress, Dislocation, FCC structure, and Molecular dynamics simulation

Molecular dynamics simulations are used to investigate the mechanism of the homogenous dislocation nucleation stress asymmetry under applied uniaxial tensile and compressive loads in single crystals Cu, Au, Ni and Ni3Al. The effect of temperature on the homogeneous dislocation nucleation stress and the ratio of tension-compression asymmetry are studied; furthermore, the ratios of tension-compression asymmetry are carefully investigated in term of unstable stacking fault energy and the atomic stacking configurations of the {111} slip planes. It is found that the tension-compression asymmetry of the homogenous dislocation nucleation stress can be attributed to that the atomic stacking configurations of the {111} slip planes are not symmetrical about the [110] axis, which leads to nucleate different types of leading partial dislocations during compression and tension.

Crystallography, Cristallographie cristallogenèse, Geology, Géologie, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Propriétés thermiques, Thermal properties of condensed matter, Propriétés thermiques des solides cristallins, Thermal properties of crystalline solids, Dilatation thermique ; effet thermomécanique et densité, Thermal expansion; thermomechanical effects and density, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Propriétés optiques, spectroscopie et autres interactions de la matière condensée avec les particules et le rayonnement, Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation, Propriétés optiques des matériaux massifs et des couches minces, Optical properties of bulk materials and thin films, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Méthodes de croissance cristalline; physique de la croissance cristalline, Methods of crystal growth; physics of crystal growth, Croissance en solution, Growth from solutions, Sciences appliquees, Applied sciences, Electronique, Electronics, Electronique des semiconducteurs. Microélectronique. Optoélectronique. Dispositifs à l'état solide, Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices, Electronique moléculaire, nanoélectronique, Molecular electronics, nanoelectronics, Analyse thermique différentielle, Differential thermal analysis, Calorimétrie différentielle balayage, Differential scanning calorimetry, Composé organique, Organic compounds, Croissance cristalline, Crystal growth, Diffraction RX, XRD, Dureté Vickers, Vickers hardness, Electronique moléculaire, Molecular electronics, Etude expérimentale, Experimental study, Etude théorique, Theoretical study, Evaporation, Monocristal, Monocrystals, Morphologie cristalline, Crystal morphology, Méthode en solution, Growth from solution, Método en solución, Méthode fonctionnelle densité, Density functional method, Orbitale moléculaire, Molecular orbital, Orbital molecular, Potentiel électrostatique, Electrostatic potential, Potencial electrostático, Propriété optique, Optical properties, Propriété thermique, Thermal properties, Propriété électronique, Electronic properties, Propiedad electrónica, Résistance mécanique, Mechanical strength, Résonance magnétique nucléaire, Nuclear magnetic resonance, Spectrométrie Raman, Raman spectroscopy, Spectrométrie transformée Fourier, Fourier transform spectroscopy, Structure cristalline, Crystal structure, Thermogravimétrie, Thermogravimetry, 6540D, A1. Characterization, A1. Crystal morphology, A1. Crystal structure, A1. X-ray diffraction, A2. Growth from solutions, and B1. Organic compounds

The 8-hydroxyquinolinium 3,5-dinitrobenzoate crystals were grown using slow evaporation solution technique. The structure was confirmed by single crystal X-ray diffraction and nuclear magnetic resonance analyses. The Fourier transform infrared and Raman spectral analyses were carried out to identify the various functional groups present in the title crystal. The optical properties were investigated by means of ultraviolet-visible spectroscopy and Kurtz―Perry powder method. Thermal properties were characterized by thermogravimetry, differential thermal analysis and differential scanning calorimetry. The mechanical strength of the crystal was investigated by Vickers microhardness tester. Additionally, first-order hyperpolarizability, nuclear magnetic resonance, molecular orbitals, electronic excitation and electrostatic potential were calculated theoretically by density functional theory using Gaussian 03 program package. .

Chemical industry parachemical industry, Industrie chimique et parachimique, Mechanics acoustics, Mécanique et acoustique, Metallurgy, welding, Métallurgie, soudage, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines classiques de la physique (y compris les applications), Fundamental areas of phenomenology (including applications), Mécanique des solides, Solid mechanics, Mécanique des structures et des milieux continus, Structural and continuum mechanics, Elasticité statique (thermoélasticité...), Static elasticity (thermoelasticity...), Etude théorique, Theoretical study, Estudio teórico, Matériau composite, Composite material, Material compuesto, Matériau fibre unidirectionnelle, Unidirectional fiber material, Material fibra unidireccional, Matériau renforcé fibre, Fiber reinforced material, Material reforzado fibra, Micromécanique, Micromechanics, Module cisaillement, Shear modulus, Módulo cizalladura Coulomb, Modèle mécanique, Mechanical model, Modelo mecánico, Modélisation, Modeling, Modelización, Propriété mécanique, Mechanical properties, Propiedad mecánica, Simulation numérique, Numerical simulation, Simulación numérica, Solution analytique, Analytical solution, Solución analítica, A. Fibres, B. Elasticity, C. Analytical modelling, C. Micro-mechanics, and Symmetry

Unidirectional fibre-reinforced composites with symmetrical structure, loaded by transverse shear, are investigated. The focus of the paper is on mathematical models for different representative cells. Transverse shear of symmetrical composites, unlike other types of loads, does not allow application of Curie's principle for detection of possible symmetry of mechanical fields. The existence of such symmetry is shown by employing the theorem proven earlier by the author. Respective boundary value problems can be formulated for the minimal representative cell. In contrast to the existing approach, which contains inaccuracy of Saint―Venant's principle, the proposed formulations are exact. It is shown that employing the symmetry cell in numerical solutions can reduce computational cost by 2―3 orders. With the use of Lagrange's and Castigliano's variational principles in generalised form, it is proven that solutions for the infinite cell give lower and upper bounds for the transverse shear modulus. It is proven, as well, that these bounds lie within the Voigt and Reuss bounds.

Crystallography, Cristallographie cristallogenèse, Electronics, Electronique, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Surfaces et interfaces; couches minces et trichites (structure et propriétés non électroniques), Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties), Surfaces solides et interfaces solide-solide, Solid surfaces and solid-solid interfaces, Adsorption, Calcul ab initio, Ab initio calculations, Couche mince, Thin films, Dioxyde d'azote, Nitrogen dioxide, Nitrógeno dióxido, Etat surface, Surface states, Etude théorique, Theoretical study, Lacune, Vacancies, Méthode dynamique moléculaire, Molecular dynamics method, Bi2Te3, Isolant topologique, Topological insulator, Dirac cone, gas adsorption, and surface band tuning

The surface band tuning of the topological insulator Bi2Te3 by gas adsorption is investigated on the basis of ab initio calculations. It is shown that, with the increase of Te vacancies, the topologically non-trivial surface state which originates from the second quintuple layer coexists with the topologically trivial surface. Molecular dynamics simulation reveals that O2 and NO2 easily occupy the Te vacancy sites and further bind to the Bi atoms from the second atomic layer. Moreover, the surface band with the Dirac cone is observed. Our results suggest that the topological surface state can be effectively regulated by NO2 and O2 adsorption.