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General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Cristaux liquides, Liquid crystals, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Etats électroniques, Electron states, Phénomènes collectifs, Collective effects, Echange, corrélation, réponses diélectrique et magnétique, plasmons, Exchange, correlation, dielectric and magnetic functions, plasmons, 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, Photoluminescence, 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, Antenne, Antennas, Couche mince, Thin films, Cristal liquide, Liquid crystals, Echelle nanométrique, Nanometer scale, Fluorescence, Luminescence, Modulation, Nanostructure, Nanostructures, Nanoélectronique, Nanoelectronics, Plasmon, Plasmons, Plasmonique, Plasmonics, Propriété optique, Optical properties, Source lumière, Light sources, Système actif, Active system, Sistema activo, 7145G, Nanoantenne, Nanoantenna, and Nanoantena

We propose a tunable plasmonic nanoantenna design that achieves steering fluorescence beams via a voltage signal. The configuration is composed of a nanometallic grating structure coated with a thin luminescent layer and a liquid crystals (LC) cell fixed above as a modulator. The angle-scanned fluorescence spectra show that fluorescence emitted from this metallic grating antenna has a high directivity (divergence angle ≈ 3°) and the beams present a high monochromaticity (full width at half-maximum ≈ 14 nm). More importantly, the fluorescence wavelength can be continuously tuned at a high repetition rate according to the electric signal applied on the LC modulation layer. We further extended the tunable antenna design to a bullseye-shaped nanoantenna to achieve tunable complete-collimated beams. The active control strategy of luminescence based on plasmonic nanoantennas has a great practical significance in developing novel tunable nanoscale light sources.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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 et équipements généraux, General equipment and techniques, Capteurs (chimiques, optiques, électriques, de mouvement, de gaz, etc.); télédétection, Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, 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, Etats électroniques de surface et d'interface, Surface and interface electron states, Excitations collectives (incluant excitons, polarons, plasmons et autres excitations de densité de charge), Collective excitations (including excitons, polarons, plasmons and other charge-density excitations), 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 structures de basse dimensionnalité, mésoscopiques, des nanostructures et nanomatériaux, Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures, Acrylamide dérivé polymère, Acrylamide derivative polymer, Acrilamida derivado polímero, Biodétecteur, Biosensors, Couche mince, Thin films, Fluorescence, Gonflement, Swelling, Hydrogel, Hidrogel, Indice réfraction, Refractive index, Multiplexage, Multiplexing, Oxyde d'indium, Indium oxide, Indio óxido, Oxyde d'étain, Tin oxide, Estaño óxido, Plasmon surface, Surface plasmons, Propriété optique, Optical properties, Résonance plasmon surface, Surface plasmon resonance, Spectrométrie fluorescence, Fluorescence spectroscopy, 0707D, and 7320M

The use of thermoresponsive poly(N-isopropylacrylamide)-based hydrogel (pNIPAAm) for rapid tuning of surface plasmon resonance (SPR) is reported. This approach is implemented by using an SPR layer architecture with an embedded indium tin oxide microheater and pNIPAAm film on its top. It takes advantage of rapid thermally induced swelling and collapse of pNIPAAm that is accompanied by large refractive index changes and leads to high thermo-optical coefficient of dn/dT = 2 × 10-2 RIU/K. We show that this material is excellently suited for efficient control of refractive index-sensitive SPR and that it can serve simultaneously as a 3D binding matrix in biosensor applications (if modified with biomolecular recognition elements for a specific capture of target analyte). We demonstrate that this approach enables modulating of the output signal in surface plasmon-enhanced fluorescence spectroscopy biosensors and holds potential for simple time-multiplexing of sensing channels for parallelized readout of fluorescence assays.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Réactions catalytiques, Catalytic reactions, Addition azote, Nitrogen addition, Adición nitrógeno, Dopage, Doping, Eau, Water, Agua, Microscopie électronique transmission, Transmission electron microscopy, Microscopía electrónica transmisión, Microstructure, Microestructura, Nanoparticule, Nanoparticle, Nanopartícula, Oxydation, Oxidation, Oxidación, Oxyde de zinc, Zinc oxide, Zinc óxido, Photocatalyse, Photocatalysis, Fotocatálisis, Rayonnement visible, Visible radiation, Radiación visible, Spectre photoélectron RX, X-ray photoelectron spectra, and ZnO

Nitrogen-doped ZnO bundle-like nanoparticles were prepared by heating ZnOHF precursor at different temperatures under an ammonia atmosphere. ZnOHF gradually transformed to N-ZnO with the increase of the heating temperature, and the as-prepared N-ZnO nano-particles preserved the original morphologies of ZnOHF at moderate heating temperature. The N-ZnO nanoparticles demonstrated drastically enhanced absorption in the visible region compared with the commercial ZnO and N-ZnO derived from commercial ZnO. Theoretical calculations indicated that the contribution of nitrogen to the top of the valence band (VB) of ZnO plays the major role of extending the absorption of ZnO to the visible region. The as-prepared N-ZnO showed high photocatalytic activity for the visible-light-induced water oxidation, and the activity can be further greatly enhanced by loading IrO2 cocatalyst. To our knowledge, this is the first report of realizing photocatalytic water oxidation on non-metal-doped ZnO under visible light without applied bias, thus adding new value to the band gap engineering of benchmark ZnO for efficient solar energy utilization.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Méthodes de nanofabrication, Methods of nanofabrication, Méthodes catalytiques, Catalytic methods, Activité catalytique, Catalyst activity, Actividad catalítica, Adsorption, Cinétique réaction, Reaction kinetics, Clivage, Cleavage, Dépendance température, Temperature dependence, Liaison carbone carbone, Carbon carbon bond, Enlace carbono carbono, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Méthane, Methane, Oxydation, Oxidation, Palladium, Réaction catalytique, Catalytic reaction, Reacción catalítica, and 8116H

The temperature-dependent adsorption as well as the possible activation and dehydrogenation of methane mediated by small free palladium Pdx+ (x = 2―4) and palladium mono-oxide PdxO+ (x = 2―4) clusters have been studied in an ion trap experiment under multicollision conditions. The smallest clusters Pd2+ and Pd3+ are found to readily dehydrogenate methane, while Pd4+ is completely nonreactive within the whole investigated temperature range between 220 and 300 K. In the case of the oxides PdxO+, a critical number of at least three coadsorbed CD4 is required before methane dehydrogenation can be observed. Temperature-dependent kinetic studies of the reaction of Pd2+ and Pd2O+ with methane allow for the determination of catalytic reaction mechanisms that involve C―D bond cleavage and C―C bond formation processes. The catalytic activity of these two clusters is compared in terms of active species, cooperative effects, and activation barriers. Finally, the possible methane oxidation on PdxO+ is discussed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Acroléine, Acrolein, Acroleína, Adsorption, Adsorción, Chaleur adsorption, Heat of adsorption, Calor adsorción, Hydrogénation, Hydrogenation, Hidrogenación, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Méthode fonctionnelle densité, Density functional method, Nickel, Niquel, Spin polarisé, Polarized spin, and Spin polarizado

Acrolein hydrogenation via allyl alcohol, propanal, and enol into propanol on the Ni(111) surface has been investigated using the spin-polarized periodic density functional theory method. On the basis of the computed adsorption energies and effective hydrogenation barriers, acrolein hydrogenation into propanal and allyl alcohol obeys the Langmuir―Hinshelwood mechanism and propanal formation is more favored kinetically and thermodynamically than allyl alcohol formation. Hydrogenation of propanal and allyl alcohol should follow the Eley―Rideal mechanism. The adsorption energies of acrolein, allyl alcohol, and propanal along with the partial hydrogenation selectivity on Ni, Au, Ag, and Pt catalysts have been compared and discussed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Propriétés de transport (non électroniques), Transport properties of condensed matter (nonelectronic), Diffusion dans les solides, Diffusion in solids, 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, Activation thermique, Thermal activation, Termoactivación, Barrière diffusion, Diffusion barriers, Couche mince, Thin films, Croissance film, Film growth, Diffusion superficielle, Surface diffusion, Diffusion(transport), Diffusion, Effet contrainte, Stress effects, Etat adsorbé, Adsorbed state, Estado adsorbido, Etat vibrationnel, Vibrational states, Etude théorique, Theoretical study, Loi échelle, Scaling laws, Méthode Monte Carlo, Monte Carlo methods, Méthode dynamique moléculaire, Molecular dynamics method, Onde acoustique surface, Acoustic surface waves, Onde acoustique, Acoustic waves, Phénomène transitoire, Transients, Simulation numérique, Digital simulation, Traitement surface, and Surface treatments

The idea of acoustic activation of surface diffusion is explored theoretically and in atomistic simulations. It is found that a substantial diffusion enhancement by surface acoustic waves is possible via (1) transient surface strain-induced modification of the diffusion barriers, (2) adiabatic variation in the surface temperature, and (3) dynamic coupling of the acoustic waves with vibrational states of adsorbed species. The approximate scaling laws describing the first two effects are established and verified in kinetic Monte Carlo simulations. The combined contribution of all three effects is studied in molecular dynamics simulations, and the conditions for the diffusion activation through the dynamic coupling are elucidated. The acoustic enhancement of surface diffusion provides an attractive alternative to thermal activation in thin film growth on heat-sensitive substrates.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Acétate, Acetates, Acétylène, Acetylene, Adsorption, Clivage, Cleavage, Couche mince, Thin films, Dépendance température, Temperature dependence, Déshydrogénation, Dehydrogenation, Désorption, Desorption, Enolate, Enolato, Ethylène, Ethylene, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Réaction surface, Surface reactions, and CeO2-x

This study reports and compares the adsorption and dissociation of acetaldehyde on oxidized and reduced CeOx(100) thin films. Acetaldehyde reacts and decomposes on fully oxidized CeO2(100), whereas it desorbs molecularly at low temperature on CeO2(111). The primary products are CO, CO2, and water along with trace amounts of crotonaldehyde and acetylene. The acetaldehyde adsorbs as the η2-acetaldehyde species, dioxyethylene. Decomposition proceeds by dehydrogenation through acetate and enolate intermediates. The reaction pathway is similar on the reduced CeO2―x(100) surface; however, the inability to react with surface O on the reduced surface results in H2 rather than H2O desorption, and C is left on the surface rather than producing CO and CO2. C―O bond cleavage in the enolate intermediate followed by reaction with surface H results in ethylene desorption.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Structure et rugosité d'interface, Interface structure and roughness, Accommodation réseau, Mismatch lattice, Acomodación red, Composé organique, Organic compounds, Couche autoassemblée, Self-assembled layers, Couche tampon, Buffer layer, Capa tampón, Couche ultramince, Ultrathin films, EXAFS, Microscopie tunnel balayage, Scanning tunneling microscopy, Modification chimique, Chemical modification, Modificación química, Méthode fonctionnelle densité, Density functional method, Or, Gold, Spectre photoélectron RX, X-ray photoelectron spectra, Structure interface, Interface structure, Thiol, Thiols, and XANES

The structure of self-assembled monolayers (SAMs) of 3-(4'-(methylthio)-[1,1'-biphenyl]-4-yl)propane-1-thiol (CH3S(C6H4)2(CH2)3SH) formed on Au(111)/mica has been investigated by scanning tunneling microscopy (STM), high-resolution X-ray photoemission spectroscopy (HRXPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT) calculations. A highly crystalline monolayer terminated by thioether moieties is formed, which adopts a structure that differs from the previously studied CH3 terminated analogue with its 2√3 × √3 unit cell. An oblique 2√3 X √61 chiral unit cell containing 8 molecules is proposed. Accommodation of the substantial mismatch between the lattices of the SAM and substrate is explained by molecular design. Serving as a buffer layer, the alkane spacer decouples the SAM lattice, defined by the functionalized aromatic moieties, from the substrate.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Matériaux particuliers, Specific materials, Matériaux poreux; matériaux granulaires, Porous materials; granular materials, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Echange d'ions, Ion-exchange, Adsorption, Adsorción, Diffusion(transport), Diffusion, Hydroxyde, Hydroxides, Hidróxido, Matériau poreux, Porous material, Material poroso, Métal transition, Transition metal, Metal transición, Oxydoréduction, Oxidation reduction, Oxidación reducción, Pyridine, Piridina, Site actif, Active site, Lugar activo, Zéolite, Zeolite, Zeolita, and 8105R

Accessibility studies of add sites in zeolites involving quantitative IR measurements with hindered pivalonitrile as probe molecule were performed. The extinction coefficients of the diagnostic bands of pivalonitrile interacting with Brønsted and Lewis acid sites were determined by using several zeolites structures of different concentrations and acid strength of sites. The accessibility factor (AF) was defined as the ratio of the concentrations of acid sites accessible to pivalonitrile and sites interacting with pyridine. The AF can be applied to both Brønsted and Lewis sites, whereas the methods proposed in previous works were limited only to Bronsted sites. Moreover, this method can also be applied to the accessibility studies of transition-metal cations being active sites in redox reactions. The AF suitability for accessibility studies was investigated for desilicated zeolites HZSM-S of medium and high Si/Al ratio treated with NaOH and NaOH/tetrabutylammonium hydroxide. The correlation between the values of mesopore surfaces and AFs for both Bronsted and Lewis sites in highly siliceous zeolites was observed. In more extensively desilicated zeolites, all of the acid sites were accessible to pivalonitrile, that is, AF = 1. Thereby, we assume that pivalonitrile can react not only with sites on external surfaces and in micropore mouths, as generally accepted, but small amounts of pivalonitrile can also migrate inside micropores. In desilicated zeolites with the extended mesopore system smaller fragments of micropores between two mesopores are preserved, which results in shorter average length of micropores. It facilitates the migration of pivalonitrile, and the sites inside micropores became accessible to bulky molecule. The accessibility of Lewis acid sites in desilicated zeolites is even more enhanced than that of Bronsted sites. Taking into consideration the fact that in desilicated zeolites the majority of Lewis sites originate from dehydroxylation of the Si―OH―Al groups, previously formed by the reinsertion of Al extracted from zeolite during alkaline treatment, their high accessibility is reasonable. Those newly formed Lewis sites are situated on mesopore surfaces, which facilitates accessibility to bulky molecules.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, 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, 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, Photoluminescence, 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, Acrylamide dérivé polymère, Acrylamide derivative polymer, Acrilamida derivado polímero, Croissance cristalline en solution, Crystal growth from solutions, Diffusion moléculaire, Molecular diffusion, Difusión molecular, Fluorescence, Mouvement moléculaire, Molecular motion, Méthode contrôle, Control method, Método control, Pistage, Tracking, Rastreo, Polymère, Polymers, Solution aqueuse, Aqueous solutions, Spectrométrie fluorescence, Fluorescence spectroscopy, Séparation phase, Phase separation, and 8110D

We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Propriétés de transport (non électroniques), Transport properties of condensed matter (nonelectronic), Diffusion dans les solides, Diffusion in solids, 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, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Généralités, appareillage, General, apparatus, Absorption optique, Optical absorption, Absorción óptica, Anatase, Anatasa, Bande absorption, Absorption band, Banda absorción, Catalyseur, Catalyst, Catalizador, Diffusion(transport), Diffusion, Déplacement raie, Spectral line shift, Desplazamiento raya espectral, Etude théorique, Theoretical study, Estudio teórico, Génération porteur charge, Charge carrier generation, Generación portador carga, Méthode fonctionnelle densité, Density functional method, Photocatalyse, Photocatalysis, Fotocatálisis, Photoexcitation, Phénomène transitoire, Transients, Fenómeno transitorio, Piégeage porteur charge, Charge carrier trapping, Captura portador carga, Spectre absorption, Absorption spectrum, Espectro de absorción, Transfert charge, Charge transfer, Transferencia carga, Transport charge, Charge transport, and 7115M

Charge transport to surface reactive sites is a crucial step in any photocatalytic process. In the most popular photocatalyst—the anatase TiO2―this step is complicated by the fact that photogenerated carriers can trap. Studies of charge trapping and transfer in anatase often employ transient absorption spectroscopy (TAS), but the understanding of the optical absorption due to trapped carriers in TiO2 is incomplete. On the basis of the generalized Δ self-consistent field density functional theory (Δ-SCF DFT) calculations, we attribute the experimentally observed absorption band at 430―550 nm to the interpolaron transitions of the stable surface and subsurface O― centers and associate the blue shift of the spectra after the photoexcitation with holes migration to surfaces. We also suggest that subsurface hole trapping may contribute to generally lower photocatalytic performance of the anatase (101) surface compared to the (001) surface.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, 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, Transport électronique, Electronic transport in condensed matter, Conductivité de matériaux particuliers, Conductivity of specific materials, Conduction limitée charge espace, Space-charge-limited conduction, Conductivité type p, P type conductivity, Conductividad tipo p, Conductivité électronique, Electronic conductivity, Conductividad electrónica, Couche mince, Thin films, Diamine, Diamina, Distribution courant, Current distribution, Dépendance température, Temperature dependence, Effet champ électrique, Electric field effects, Electron conduction, Conduction electron, Electrón conducción, Mobilité trou, Hole mobility, Piégeage porteur charge, Charge carrier trapping, Captura portador carga, Semiconducteur organique, Organic semiconductors, Température électron, Electron temperature, Transport charge, and Charge transport

Charge transport is important both in the research and application of organic semiconductors. For hole transport materials, most works focus on the transport characteristics of holes while less attention is paid to that of electrons. In this study, electron currents in N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD) thin films were studied. It is found that temperature dependence of electron conduction of TPD varies with driving voltage: in low voltage range, the electron conduction increases with temperature, while in the high voltage range it decreases abnormally with increasing temperature. Neither trapped-charge-limited current with exponential distribution of traps nor trap free space-charge-limited current with electric-field-dependent mobility could be used to interpret all the observed phenomena. The inability of current models to explain the phenomena indicates that the electron transport mechanism of TPD is different from that of holes.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, 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, 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, Structure électronique des nanomatériaux : agrégats, nanoparticules, nanotubes et nanocristaux, Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals, Calcul ab initio, Ab initio calculations, Dérivé du biphényle, Biphenyl derivatives, Bifenilo derivado, Déshydrogénation, Dehydrogenation, Graphène, Graphene, Hydrogénation, Hydrogenation, Matériau poreux, Porous materials, Mode vibration, Vibrational modes, Méthode fonctionnelle densité, Density functional method, Optique non linéaire, Nonlinear optics, Polarisabilité, Polarizability, Propriété optique, Optical properties, Spectre IR, Infrared spectra, Spectre Raman, Raman spectra, Théorie quantique, and Quantum theory

We present a detailed periodic ab initio quantum-mechanical simulation of two recently proposed systems, namely hydrogenated porous graphene (HPG) and biphenyl carbon (BPC), using hybrid HF-DFT functionals and all-electron Gaussian-type basis sets. The equilibrium geometry, the vibrational spectrum (including IR intensities), the full set of components of the polarizability and hyperpolarizability tensors are provided, the latter evaluated through a coupled-perturbed KS/HF scheme. IR and Raman spectra for the two systems are quite different, and differ also from graphene, thus permitting their experimental identification. It is then shown that small defects inserted into the graphene sheet lead to finite values for the in-plane components of the static (hyper)polarizability tensors, spanning a relatively large range of values. By dehydrogenation of porous graphene into biphenyl carbon, a noteworthy enhancement of the nonlinear optical properties through the static second dipole hyperpolarizability can be achieved. Vibrational contributions to the polarizability are negligible for both systems.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, 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, 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, Etats électroniques de surface et d'interface, Surface and interface electron states, Etats de surface, structure de bande, densité d'états électroniques, Surface states, band structure, electron density of states, 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, Fullerènes et matériaux apparentés; diamants, graphite, Fullerenes and related materials; diamonds, graphite, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Divers, Other topics in nanoscale materials and structures, Calcul ab initio, Ab initio calculations, Carbone, Carbon, Chimie surface, Surface chemistry, Etude théorique, Theoretical study, Fonctionnalisation, Functionalization, Funciónalización, Graphène, Graphene, Maille cristalline, Unit cell, Mode vibration, Vibrational modes, Modification chimique, Chemical modification, Modificación química, Méthode fonctionnelle densité, Density functional method, Nanostructure, Nanostructures, Résultat expérimental, Experimental result, Resultado experimental, Spectre IR, Infrared spectra, Spectre Raman, Raman spectra, Structure électronique, Electronic structure, Vibration, Vibrations, 7320A, 8105T, and 8105U

The present work reports a theoretical study of the infrared (IR) and Raman spectra of chemical structures that are useful for the description of the surface chemistry of carbon materials. There has been a recent demand in materials science and surface functionalization to couple organic entities with sp2 carbon nanostructures. A slab model of single-layer graphene with its edges terminated by hydrogen atoms containing 82 atoms per unit cell was used in our study. The organic coupling agent, perfluorophenylazide (PFPA), was used according to a recent experiment [Liu, L.-H.; et al.et al. Nano Lett. 2010, 10, 3754]. Two ab initio DFT functionals, B3LYP and ωB97XD, were adopted to calculate the IR and Raman spectra. The computational approach was tested by comparing the calculated IR spectra to those obtained experimentally for various reference compounds. The vibrational features were probed before and after the reaction, and the changes, arising in both PFPA and graphene spectra as a result of the coupling, were identified. B3LYP gave better agreement with the experimental results than ωB97XD for frequency calculations. The stretch modes of the azide group, as well as the fingerprint feature of the CF2 axial stretching vibrations, were used to probe the reaction, and the results were in good agreement with the experimental observations. Special attention was paid to the elucidation of the origins of the G-, D-, and D'-bands in the Raman spectra of graphene. Finally, the predicted assignments were employed to interpret the IR and Raman spectra obtained experimentally for functionalized graphenes.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Propriétés mécaniques et acoustiques de l'état condensé, Mechanical and acoustical properties of condensed matter, Propriétés mécaniques des nanostructures et des nanomatériaux, Mechanical properties of nanoscale materials, 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, Calcul ab initio, Ab initio calculations, Electronégativité, Electronegativity, Force électrostatique, Electrostatic force, Fuerza electrostática, Frottement, Friction, Graphène, Graphene, Interaction van der Waals, Van der Waals interaction, Interacción van der Waals, Interaction électrostatique, Electrostatic interaction, Interacción electrostática, Lubrifiant, Lubricants, Méthode fonctionnelle densité, Density functional method, and Graphane

The atomic-scale friction in fluorographene and graphane is investigated employing the density functional theory calculation including the dispersion correction (DFT-D). Fluorographene and graphane exhibit low friction because of the low interlayer interaction induced by the repulsive electrostatic forces between F or H atoms at the interfaces. Moreover, owing to the less electronegativity of H atoms than F atoms, the variation of interlayer spacing and system energy corrugation, which is predominantly determined by the variation of dispersion energy during both loading and sliding processes, as elucidated in this paper, is found to be much larger in graphane, which well explains the larger friction in graphane than in fluorographene. The more charged F atom in fluorographene diminishes the variation of the interlayer spacing, which finally decreases the variation of the dispersion energy in the fluorographene. The study theoretically reveals the general mechanism of atomic-scale friction in various graphene-based layered materials where the interlayer interaction is dominated by van der Waals and electrostatic interactions, which shed light on friction reduction and the design of new lubricant materials.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Structure et topographie de surface, Surface structure and topography, Calcul ab initio, Ab initio calculations, Chaleur formation, Heat of formation, Energie surface, Surface energy, Fluorure de calcium, Calcium fluoride, Calcio fluoruro, Interaction coulombienne, Coulomb interaction, Interacción coulombiana, Méthode fonctionnelle densité, Density functional method, Oxyde de cérium, Cerium oxide, Cerio óxido, Structure atomique, Atomic structure, Structure fluorite, Fluorite structure, Estructura fluorita, Structure surface, Surface structure, CaF2, and CeO2

Utilizing first-principle simulations [based on density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U)], we develop a model to explain the experimental stability in solution of materials having the fluorite structure, such as CaF2 and CeO2. It is shown that the stability of a surface is mainly dependent on its atomic structure and the presence of sites where atoms are deficiently bonded. Using as reference planes the surfaces with low surface formation energies, viz., (111), (100), and (110), our results reveal the relation between the surface energy of any Miller-indexed plane and the surface energy of those reference planes, being dependent on the fluorite surface structure only. Therefore, they follow the same trend for CaF2 and CeO2. Comparison with experimental results shows a correlation between the trends of dry surface energies and surface stabilities during dissolution of both CaF2 and CeO2, even though the chemical processes of dissolution of CeO2 and CaF2 are different. A deviation between ab initio predictions and experiments for some surfaces highlights the sensitivity of the developed model to the treatment of surface dipolar moments.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, 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, Transport électronique, Electronic transport in condensed matter, Conductivité de matériaux particuliers, Conductivity of specific materials, Polymères; composés organiques (incluant les semiconducteurs organiques), Polymers; organic compounds (including organic semiconductors), 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, Constantes optiques: indice de réfraction; constante diélectrique complexe; coefficients d'absorption, de réflexion et de transmission; émissivité, Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity, Sciences appliquees, Applied sciences, Energie, Energy, Energie naturelle, Natural energy, Energie solaire, Solar energy, Conversion photovoltaïque, Photovoltaic conversion, Cellules solaires. Cellules photoélectrochimiques, Solar cells. Photoelectrochemical cells, Calcul ab initio, Ab initio calculations, Cellule solaire, Solar cells, Cristal moléculaire, Molecular crystals, Dérivé du thiadiazole, Thiadiazole derivatives, Tiadiazol derivado, Exciton, Excitons, Force oscillateur, Oscillator strengths, Hétérostructure, Heterostructures, Mobilité porteur charge, Carrier mobility, Spectre absorption, Absorption spectra, Structure moléculaire, Molecular structure, Structure électronique, and Electronic structure

Using ab initio methods we examine the molecular and solid-state electronic properties of a recently synthesized small-molecule donor, p-DTS(PTTh2)2, which belongs to the dithienosilole-pyridylthiadiazole family of chromophores. In combination with the PC70BM acceptor, p-DTS(PTTh2)2 can be used to fabricate high-efficiency bulk heterojunction organic solar cells. A precise picture of molecular structure and interchromophore packing is provided via a single-crystal X-ray diffraction study; such details cannot be easily obtained with donor materials based on conjugated polymers. In first-principles approaches we are limited to a single-crystallite scale. At this scale, according to our investigation, the principal properties responsible for the high efficiency are strong low-energy light absorption by individual molecules, large exciton diffusion length, and fast disorder-resistant hole transport along π-stacks in the crystallite. The calculated exciton diffusion length is substantially larger than the average crystallite size in previously characterized device active layers, and the calculated hole mobility is 2 orders of magnitude higher than the measured device-scale mobility, meaning that the power conversion losses on a single-crystallite scale are minimal.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Nanomatériaux : agrégats, nanoparticules, nanotubes et nanocristaux, Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, 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, Structure électronique des nanomatériaux : agrégats, nanoparticules, nanotubes et nanocristaux, Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals, Agrégat atomique, Atomic clusters, Agrégat solide, Solid clusters, Calcul ab initio, Ab initio calculations, Carbone, Carbon, Densité charge, Charge density, Délocalisation électronique, Electron delocalization, Deslocalización electrónica, Energie cinétique, Kinetic energy, Etat localisé, Localized states, Liaison chimique, Chemical bonds, Métal transition, Transition elements, Méthode dynamique moléculaire, Molecular dynamics method, Méthode fonctionnelle densité, Density functional method, Nanoamas, Nanocluster, Nanomontón, Titane, and Titanium

The dynamics of the collision process of a titanium dimer against a C20 nanocluster in the bowl configuration is simulated by means ab initio molecular dynamics, focusing our interest on the first steps to synthesize Ti2C20 clusters, characterizing the relevant structures generated during the collision process. The electronic localization function is also calculated. The early stages of the dynamics are critical to determine the outcome because of the large kinetic energy of the Ti dimer, which allows it to wander around the C20 cluster.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Matériaux nanocristallins, Nanocrystalline materials, Nanotubes, Méthodes de nanofabrication, Methods of nanofabrication, Méthodes catalytiques, Catalytic methods, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Généralités, appareillage, General, apparatus, Alcool, Alcohols, Calcul ab initio, Ab initio calculations, Catalyseur, Catalysts, Dynamique moléculaire, Molecular dynamics, Dinámica molecular, Dépôt chimique phase vapeur filament chaud, Hot filament chemical vapor deposition, Depósito químico fase vapor filamento caliente, Energie activation, Activation energy, Energie liaison, Binding energy, Ethanol, Ethylène, Ethylene, Etude théorique, Theoretical study, Liaison carbone carbone, Carbon carbon bond, Enlace carbono carbono, Molécule de carbone, Carbon molecules, Monoxyde de carbone, Carbon monoxide, Carbono monóxido, Méthane, Methane, Méthode dynamique moléculaire, Molecular dynamics method, Nanomatériau, Nanostructured materials, Nanotube carbone, Carbon nanotubes, Nickel, Produit réaction, Reaction product, Producto reacción, Simulation numérique, Digital simulation, Synthèse nanomatériau, Nanomaterial synthesis, Síntesis nanomaterial, 8107B, 8107D, and 8116H

The dissociation of ethanol molecules on a nickel cluster was investigated by ab initio molecular dynamics and nudged-elastic-band (NEB) simulations to discuss the initial stage of metal-catalyzed growth of carbon nanotubes via alcohol catalytic chemical vapor deposition. Both C― C and C―O bonds in ethanol molecules are dissociated on the nickel cluster, which is followed by the formation of various reaction products such as hydrogen atoms and molecules, carbon monoxide, oxygen atoms, water, ethylene, methane, and their fragments. Moreover, the NEB analysis revealed that the activation energy for C―H bond dissociation in the fragment molecules on the nickel cluster is just approximately one-eighth of the bond-dissociation energy of the corresponding C―H bond without the influence of the nickel cluster. This confirms that the nickel cluster acts as the activator of the dissociation process of carbon-source molecules by reducing the activation energy.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, 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), Structures de basse dimensionnalité (superréseaux, puits quantiques, multicouches): structure et propriétés non électroniques, Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, 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, Structure électronique des nanomatériaux : agrégats, nanoparticules, nanotubes et nanocristaux, Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Matériaux nanocristallins, Nanocrystalline materials, Méthodes de nanofabrication, Methods of nanofabrication, Formation de nanomotifs, Nanoscale pattern formation, Bande interdite, Energy gap, Calcul ab initio, Ab initio calculations, Effet dimensionnel, Size effect, Energie propre, Self-energy, Etat excité, Excited states, Formation nanomotif, Nanopatterning, Formacíon nanomotivo, Germanium, Nanocristal, Nanocrystal, Nanomatériau, Nanostructured materials, Nanopoint, Nanodot, Nanopunto, Nanostructure, Nanostructures, Orbitale frontière, Frontier orbital, Orbital frontera, Silicium, Silicon, Structure électronique, Electronic structure, 8107B, and 8116R

Nanostructuring of a material leads to enormous effects on its excited state properties. This study, through the application of different state-of-the-art ab initio theoretical tools, investigates the effect of size on the electronic gap of germanium nanocrystals highlighting similarities and differences with respect to equivalent silicon nanostructures. We performed both GW and ΔSCF calculations for the determination of their electronic structure. While it is known that ΔSCF corrections to the Kohn―Sham gap vanish for extended systems, the two approaches were expected to be equivalent in the limit of small clusters. However, it has been recently found that for hydrogenated Si clusters the ΔSCF gaps are systematically smaller than the GW ones, while the opposite is true for Ag clusters. In this work we find that the GW gaps are larger than the ΔSCF ones for all the Ge dots, with the exception of the smallest one. Such crossing between the ΔSCF and the GW gap values was not expected and has never been observed before. Moreover, also for hydrogenated Si nanocrystals we found a similar behavior. The origin of this crossing might be found in the Rydberg character of the LUMO of the smallest clusters and can also explain the qualitative differences in the comparison between GW and ΔSCF found in the previous studies.