Literatura académica sobre el tema "NMR-GIPAW"

A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile–4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental 1H and 13C chemical shifts are determined from two-dimensional 1H–13C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C—H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a 1H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the 1H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N—H...O and C—H...O hydrogen bonding, while changes of −2.7 and −1.5 ppm are due to ring current effects associated with C—H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.

Energy barriers for Li⁺ migration in Li₂ZrO₃ as well as GIPAW NMR isotropic spectral parameters for⁷ Li were computed, aiming to provide guidance for the interpretation and prediction of spectra of more complex systems like materials for LIBs.

Computational methods are increasingly used to support interpreting, assigning and predicting the solid-state nuclear resonance magnetic spectra of materials. Currently, density functional theory is seen to achieve a good balance between efficiency and accuracy in solid-state chemistry. To be specific, density functional theory allows the assignment of signals in nuclear resonance magnetic spectra to specific sites and can help identify overlapped or missing signals from experimental nuclear resonance magnetic spectra. To avoid the difficulties correlated to all-electron calculations, a gauge including the projected augmented wave method was introduced to calculate nuclear resonance magnetic parameters with great success in organic crystals in the last decades. Thus, we developed a gauge including projected augmented pseudopotentials of 21 d elements and tested them on, respectively, oxides or nitrides (semiconductors), calculating chemical shift and quadrupolar coupling constant. This work can be considered the first step to improving the ab initio prediction of nuclear magnetic resonance parameters, and leaves open the possibility for inorganic compounds to constitute an alternative standard compound, with respect to tetramethylsilane, to calculate the chemical shift. Furthermore, this work represents the possibility to obtain results from first-principles calculations, to train a machine-learning model to solve or refine structures using predicted nuclear magnetic resonance spectra.

In this work niobium oxide clusters on the surface of Al2O3 are modeled using DFT calculations. 93Nb NMR parameters of modeled clusters were computed with the GIPAW method. The niobia system under consideration represents high niobium loading on the surface of the support. The niobium atoms are highly coordinated and linked to the other niobia polyhedra by one or two bonds. The most of the niobium oxide particles has a coordination number of six. The correlations found between 93Nb NMR parameters and coordination environment are discussed.

The characterization of the three-dimensional structure of solids is of major importance, especially in the pharmaceutical field. In the present work, NMR crystallography methods are applied with the aim to refine the crystal structure of carbimazole, an active pharmaceutical ingredient used for the treatment of hyperthyroidism and Grave’s disease. Starting from previously reported X-ray diffraction data, two refined structures were obtained by geometry optimization methods. Experimental 1H and 13C isotropic chemical shift measured by the suitable 1H and 13C high-resolution solid state NMR techniques were compared with DFT-GIPAW calculated values, allowing the quality of the obtained structure to be experimentally checked. The refined structure was further validated through the analysis of 1H-1H and 1H-13C 2D NMR correlation experiments. The final structure differs from that previously obtained from X-ray diffraction data mostly for the position of hydrogen atoms.

We report a complete set of high-resolution solid-state NMR spectra for all magnetic nuclei (1H, 13C, 17O, and 27Al) in the α-form of tris(2,4-pentanedionato-O,O′)aluminium(III), α-Al(acac)3. These high-resolution NMR spectra were obtained by using a host of solid-state NMR techniques: standard cross-polarization under the magic-angle spinning (CPMAS) method for 13C, 1-D homonuclear decoupling using the windowed DUMBO sequence for 1H, double-rotation (DOR) for 17O and 27Al, and multiple-quantum MAS for 27Al. Some experiments were performed at multiple magnetic fields. We show that the isotropic chemical shifts obtained for 1H, 13C, 17O, and 27Al nuclei in α-Al(acac)3 are highly resolved and accurate, regardless of the nature of the targeted nuclear spins (i.e., spin-1/2 or quadrupolar) and, as such, can be treated equally in comparison with computational chemical shifts obtained from a gauge-including projector-augmented wave (GIPAW) plane-wave pseudopotential DFT method.

Solid-state 73Ge nuclear magnetic resonance (NMR) is an attractive technique for the characterization of solid germanium-containing materials, but experiments can be exceedingly difficult in practice due to the unfavourable NMR properties of the 73Ge nucleus. Presented herein is a series of solid-state 73Ge NMR experiments on germanium halides (GeX4 and GeX2, where X = I, Br, and Cl) conducted at moderate (9.4 and 11.7 T) and ultrahigh (21.1 T) magnetic fields, intended to characterize the 73Ge NMR response in highly symmetric and asymmetric coordination environments. Quadrupole coupling constants range from 0.16 to 35 MHz. Isotropic chemical shifts for the GeX4 series trend with halide electronegativity, as found for the analogous silicon and tin halides. The indirect spin-spin coupling constant 1J(73Ge, 127I) is estimated from 73Ge MAS NMR to be 35 ± 10 Hz in GeI2, with the reduced coupling constant agreeing with those of other group 14 halides. Quantum chemical calculations using GIPAW DFT are in reasonable accord with experimental quadrupole couplings, but fail for chemical shielding. A preliminary NMR crystallographic study of GeI2 and GeCl2 incorporating 127I and 35Cl NMR spectra has led to plausible conclusions reflecting the structural homology of these compounds, although definitive characterization remains elusive.

The use of ab initio Density Functional Theory (DFT) to calculate key Nuclear Magnetic Resonance (NMR) parameters has been shown to be very successful in a variety of cases. These calculations allow one to extract meaningful data from NMR measurements by providing a foundation for spectral peak assignment. However, first principle calculations for disordered systems, typically based on a single realisation of the disorder, are inadequate if the NMR parameters depend sensitively on the location of the disordered species. In this thesis, a number of different approaches for characterising disorder in solids are presented. The aim of which is to overcome current challenges regarding the computational cost of conventional supercell approaches that make it difficult to perform a direct study of the complete configurational ensemble for any supercell with a sufficient simulation cell. A case study is presented for the Ge-based apatite La7.5Ca2.5Ge6O25.75 that shows that the number of configurations one needs to consider can be vastly reduced by exploiting the symmetry of the system over a wholly enumerative approach, although exhaustive statistical averaging of the atomic positions required to reproduce the atomic resolution afforded by the solid-state NMR (ssNMR) measurement makes this problem intractable via this methodology. The sodium potassium niobate system (NaxK1-xNbO3) is studied across a series of compositions between the ordered KNbO3 and NaNbO3 end-members. This novel material exhibits purely atomic position / permutation disorder that is reflected in initial 23Na and 93Nb MAS NMR studies, but the true explanation of the disorder described by this data is not well understood. The Special Quasi-random Structure (SQS) approach to studying this disorder is presented as a computationally cheaper alternative to the supercell approach. It is noted that further studies are required to assess whether this is an adequate description of the NaxK1-xNbO3 system due the complications of modelling the complex tilting patterns exhibited by these structures. A combined ssNMR and GIPAW-DFT approach is reported to resolve the complex disorder within the vaterite polymorph of calcium carbonate. The computational data for the various structural candidates in the literature is utilised to simulate the highly sensitive DOR data, thereby elevating the predictive capability of this complementary approach to substantiate the stacking model of vaterite that views the material as a dynamic system under ambient conditions.

This thesis focuses on the determination and the modeling, by the PAW/GIPAW (Gauge Including Projector Augmented Waves) method, of NMR parameters in inorganic fluorides. In the first part, a correlation between experimental 19F isotropic chemical shift (diso) and calculated 19F isotropic shieldings (siso) of binary fluorides with obvious assignments is established that allows to predict 19F NMR spectra with a good accuracy. The quadrupolar parameters of these fluorides are also determined and calculated. In the second part, a complete and unambiguous assignment of the 19F NMR lines of NbF5 and TaF5 is obtained, ensured by the linearity between experimental 19F diso values and calculated 19F siso values. On the other hand, for the studied MF4 (b-ZrF4, HfF4, CeF4, ThF4) compounds, characterized by smaller 19F diso ranges, except for ThF4, the poor correlations between experimental 19F diso and calculated 19F siso values prevent us to propose an assignment of the 19F NMR lines. In the last part, NaAsF6 and KPF6, exhibiting large 19F-X 1J-coupling and phase transitions at temperatures close to room temperature (RT) are investigated by DTA or DSC and variable temperature X-ray powder diffraction and multinuclear solid-state NMR. The structures of a- and b-NaAsF6 are determined. KPF6 adopts a disordered high symmetry structure at RT. Unfortunately, attempts to determine the atomic positions of the two first low temperature phases remain unsuccessful. This work highlights the potentialities and some limitations of this method as well as the care that must be taken when dealing with optimized structures.

This thesis uses first principles techniques, mainly the ab initio random structure searching method (AIRSS), to study anode materials for lithium- and sodium- ion batteries (LIBs and NIBs, respectively). Initial work relates to a theoretical structure prediction study of the lithium and sodium phosphide systems in the context of phosphorus anodes as candidates for LIBs and NIBs. The work reveals new Li-P and Na-P phases, some of which can be used to better interpret previous experimental results. By combining AIRSS searches with a high-throughput screening search from structures in the Inorganic Crystal Structure Database (ICSD), regions in the phase diagram are correlated to different ionic motifs and NMR chemical shielding is predicted from first principles. An electronic structure analysis of the Li-P and Na-P compounds is performed and its implication on the anode performance is discussed. The study is concluded by exploring the addition of aluminium dopants to the Li-P compounds to improve the electronic conductivity of the system. The following work deals with a study of tin anodes for NIBs. The structure prediction study yields a variety of new phases; of particular interest is a new NaSn$_2$ phase predicted by AIRSS. This phase plays a crucial role in understanding the alloying mechanism of high-capacity tin anodes, work which was done in collaboration with experimental colleagues. Our predicted theoretical voltages give excellent agreement with the experimental electrochemical cycling curve. First principles molecular dynamics is used to propose an amorphous Na$_1$Sn$_1$ model which, in addition to the newly derived NaSn$_2$ phase, provides help in revealing the electrochemical processes. In the subsequent work, we study Li-Sn and Li-Sb intermetallics in the context of alloy anodes for LIBs. A rich phase diagram of Li-Sn is present, exhibiting a variety of new phases. The calculated voltages show excellent agreement with previously reported cycling measurements and a consistent structural evolution of Li-Sn phases as Li concentration increases is revealed. The study concluded by calculating NMR parameters on the hexagonal- and cubic-Li$_3$Sb phases which shed light on the interpretation of reported experimental data. We conclude with a structure prediction study of the pseudobinary Li-FeS$_2$ system, where FeS$_2$ is considered as a potential high-capacity electrochemical energy storage system. Our first principles calculations of intermediate structures help to elucidate the mechanism of charge storage observed by our experimental collaborators via $\textit{in operando}$ studies.

La France, ainsi que l'Europe dans son ensemble, s'engage activement dans le développement des batteries tout-solide (all solid-state batteries, SSBs), une technologie clé pour assurer la transition écologique et l'adoption massive des véhicules électriques (electric vehicles, EVs). Une avancée majeure dans ce domaine repose sur la conception et l'optimisation d'électrolytes solides (solid-state electrolytes, SSEs). Parmi les matériaux candidats, le grenat de type Lithium Lanthanum Zirconate (LLZO, Li₇La₃Zr₂O₁₂) se distingue comme un électrolyte solide prometteur pour les batteries au lithium métallique, en raison de sa stabilité chimique exceptionnelle et de sa conductivité ionique élevée. Mes travaux de thèse se concentrent sur les propriétés structurales et dynamiques du LLZO, à la fois sous sa forme pure et dopée à l'aluminium (Li₇₋₃ₓAlₓLa₃Zr₂O₁₂), en combinant des approches de simulations multi-échelles et des validations expérimentales. Dans le cadre de ma thèse, la dynamique des ions lithium a été investiguée à l'aide de méthodes théoriques avancées, incluant la théorie de la fonctionnelle de la densité (Density Functional Theory, DFT) et la dynamique moléculaire classique (Classical Molecular Dynamics, MD). Ces approches permettent de couvrir un large spectre d'échelles spatio-temporelles : des échelles atomiques (de l'ordre de l'ångström et des femtosecondes) aux échelles nanométriques et macroscopiques (impliquant jusqu'à un million d'atomes). Un outil personnalisé, MD Scrutinizer, a été développé pour analyser les mécanismes de diffusion et de migration des ions lithium, ainsi que leur confinement dans la structure cristalline. Les simulations théoriques ont été complétées par une série de techniques expérimentales, notamment la Résonance Magnétique Nucléaire (RMN), la Spectroscopie d'Impédance Électrochimique (EIS) et la diffraction des neutrons. La RMN a joué un rôle central dans l'analyse de la dynamique du lithium et de son environnement local. Les propriétés RMN ont été modélisées avec précision grâce à l'approche DFT-GIPAW (Gauge-Including Projector Augmented Wave). Une stratégie itérative combinant MD, DFT et GIPAW a été mise en œuvre pour améliorer la précision des paramètres RMN et résoudre les écarts entre les prédictions théoriques et les résultats expérimentaux. Les résultats de ma thèse mettent en évidence l'impact du dopage à l'aluminium sur les réseaux structuraux de la phase cubique de LLZO (c-LLZO), ainsi que son effet sur la dynamique des ions lithium. Ma thèse développe une méthodologie appropriée pour optimiser le LLZO et prédire les paramètres RMN dans les électrolytes solides, ouvrant la voie à une meilleure interprétation des expériences RMN, l'une des approches les plus importantes pour étudier la dynamique des ions Li. Elle contribue ainsi à la maturation des technologies de batteries tout-solide
France, along with Europe as a whole, is actively committed to the development of all-solid-state batteries (SSBs), a key technology for ensuring the ecological transition and the widespread adoption of electric vehicles (EVs). A major advancement in this field lies in the design and optimization of solid-state electrolytes (SSEs). Among the candidate materials, garnet-type LLZO (Li₇La₃Zr₂O₁₂) stands out as a promising solid electrolyte for lithium-metal batteries due to its high chemical stability and ionic conductivity. My thesis work focuses on the structural and dynamic properties of Lithium Lanthanum Zirconate (LLZO) solid-electrolyte, both in its pure and Aluminum-doped (Li₇₋₃ₓAlₓLa₃Zr₂O₁₂) forms, by combining multiscale state-of-the-art simulation methods with experimental validation. Within the framework of my thesis, lithium-ion dynamics were investigated using advanced theoretical methods, including Density Functional Theory (DFT) and Classical Molecular Dynamics (MD). These approaches cover a wide range of spatial and temporal scales: from atomic scales (on the order of ångström and femtoseconds) to nanometric and macroscopic scales (involving up to a million atoms). A custom in-house code, MD Scrutinizer, was developed to analyze lithium-ion diffusion and migration mechanisms as well as their confinement within the crystal structure. Atomistic simulations were complemented by a series of experimental techniques, including Nuclear Magnetic Resonance (NMR), Electrochemical Impedance Spectroscopy (EIS), and neutron diffraction. NMR played a central role in analyzing lithium dynamics and its local environment. NMR properties were modeled using the DFT-GIPAW (Gauge-Including Projector Augmented Wave) approach. An iterative approach combining MD, DFT, and GIPAW was proposed to enhance the predictive accuracy of NMR parameters and resolve discrepancies between theoretical predictions and NMR experimental results. The findings of my thesis highlight the impact of Aluminium doping on the structure of the cubic phase of LLZO (c-LLZO), as well as its effect on lithium-ion dynamics. The results demonstrate the interplay between structural stability, lithium diffusion pathways, and dopant-induced effects. My thesis devise the right methodology for optimizing LLZO and the prediction of NMR parameters in solid electrolytes, paving the way for a better interpretation of the NMR experiments, one of the most approach for studying Li dynamics, and contributing to advancements in all-solid-state battery technologies

Cette thèse porte sur l’étude structurale de fluorures et d'oxyfluorures, en combinant la RMN du solide, la diffraction des rayons X et les calculs PAW/GIPAW des paramètres RMN. La première partie est consacrée à l’étude des cinq composés du binaire KF-YF3. Des corrélations linéaires entre valeurs expérimentales de déplacements chimiques isotropes et de constantes d’écran isotropes calculées ont été établies pour 19F, 89Y et 39K, à partir des attributions des raies RMN aux sites cristallographiques. Ces corrélations conduisent à des accords satisfaisants. Dans le cas de 19F et 89Y, le lien entre paramètres RMN et environnement a été établie. Les paramètres RMN calculés de 39K permettent des reconstructions satisfaisantes des spectres complexes.La deuxième partie est dédiée à l’étude des deux phases ordonnées de LaOF. Les optimisations et les calculs de valence de liaison montrant que les positions atomiques de F et O devaient être inversées dans ces deux phases, leurs structures ont été réaffinées. L’accord entre paramètres RMN expérimentaux et calculés de 19F et 139La valide nos modèles structuraux. Enfin les composés MO2F (M = Nb, Ta), isotypes et désordonnés vu que les atomes de O et F occupent le même site anionique, ont été étudiés. Il est montré que la synthèse en milieu aqueux conduit à des composés hydroxylés lacunaires dont les compositions ont été déterminées en combinant RMN 19F, DRX sur poudre et ATG. La synthèse en phase solide permet d’obtenir ces composés purs. Les calculs DFT ont été réalisés sur des supermailles 3 × 3 × 3 en respectant l'ordre -M-O-M-O-M-F-. Le bon accord entre paramètres RMN de 19F expérimentaux et calculés valide les modèles proposé
This thesis focuses on the structural study of fluorides and oxyfluorides by combining solid state NMR, X-ray diffraction and PAW/GIPAW calculations of NMR parameters. The first part is devoted to the study of compounds of the KF-YF3 binary system. Linear correlation between experimental isotropic chemical shift (delta iso) and calculated isotropic shielding (sigma iso) values have been established, for 19F, 89Y and 39K, from assignments of NMR lines to crystallographic sites. These correlations lead to satisfactory agreements. In the case of 19F and 89Y, the link between NMR parameters and environment has been established. The calculated 39K NMR parameters allow satisfying reconstructions of the experimental complex spectra. The second part is dedicated to the study of the two ordered phases of LaOF. The optimizations and bond valence calculations showing that the atomic positions of F and O should be interchanged in both the phases, their structures have been refined. The agreement between experimental and calculated NMR parameters of 19F and 139La validates our structural models. Finally, the isotypic and disordered MO2F (M = Nb, Ta) compounds, since the O and F atoms occupy the same anionic site, have been studied. It is shown that the aqueous solution synthesis leads to hydroxylated and lacunary compounds, whose formulations have been determined by combining 19F NMR, XRD and TGA. The solid state synthesis enables to obtain pure compounds. DFT calculations were carried out on optimized 3 × 3 × 3 supercells that respect the partial order -M-O-M-O-M-F-. The good agreement between experimental and calculated NMR parameters of 19F validates the proposed model

Chlorine solid-state nuclear magnetic resonance (SSNMR) is an ideal site specific probe of chloride-containing solids as SSNMR tensor properties are sensitive to the local chlorine environment. In this thesis, the development and use of chlorine SSNMR as a method to characterize a wide variety of chemical environments was explored. Ultrahigh field, and multi-field studies were essential to overcome the difficulties associated with the collection of chlorine SSNMR spectra. Benchmark chemical shift (CS) and electric field gradient (EFG) tensor data were collected for organic chloride systems, including several amino acid hydrochlorides. These experiments demonstrated the sensitivity of chlorine SSNMR to slight changes in chemical environment. Quantum chemical calculations were used to complement experimental data, with the gauge-including projector augmented wave DFT (GIPAW-DFT) method shown to yield better agreement than B3LYP or RHF methods. The GIPAW-DFT method was found to slightly, but systematically, overestimate the chlorine quadrupolar coupling constant and the CS tensor span. Other organic chlorides examined by chlorine SSMR included a known ion receptor, meso-octamethylcalix[4]pyrrole. This compound was found to have a very small quadrupole interaction (QI), but significant chemical shift anisotropy (CSA). GIPAW-DFT calculations were also utilized and, in combination with the experimental results, used to identify the solvate structure of the material analyzed by NMR. Chlorine SSNMR was further used to study different solvate structures and polymorphism. The technique was an effective means to distinguish different room temperature polymorphs of benzidine hydrochloride, despite the similarities of the chloride environments. In the case of magnesium chloride, chlorine SSNMR was sensitive to the level of hydration and through the use of GIPAW-DFT calculations, the identity of an unknown hydrate was determined. An analysis of several group thirteen chlorides demonstrated that chlorine SSNMR was also capable of characterizing the chlorine environment in cases where the QI is large, despite the resulting broad line widths. In these systems GIPAW-DFT calculations also yielded excellent agreement with experimental values. Throughout this research, chlorine SSNMR has been shown to be a useful and effective means to study both organic and inorganic chlorides, with computational methods proving to be an important complement to experimental data.

NMR crystallography is the combined use of experimental solid-state nuclear magnetic resonance (NMR) with density-functional theory (DFT) calculation of NMR parameters for a structure, as obtained, for example, by complementary diffraction or crystal structure prediction (CSP) approaches. We give an overview of how NMR crystallography can be applied to active pharmaceutical ingredients (APIs) and their formulations, including considering polymorphism, solvates and hydrates, salt and co-crystal formation, and amorphous dispersions. Specifically, the use of the gauge-including projector augmented wave (GIPAW) method, as implemented, for instance, in CASTEP or Quantum Espresso, is widely employed to calculate NMR chemical shifts for nuclei such as 1H, 13C, 14/15N, 19F, and 35Cl, as well as quadrupolar parameters for spin I ≥ 1 nuclei such as 14N and 35Cl, complementing experimental data obtained using magic-angle spinning (MAS). We describe the application of key MAS NMR experiments such as cross-polarisation (CP) MAS, notably for polymorph fingerprinting and determination of the number of distinct molecules in the asymmetric unit cell (Z′), and 1H-based two-dimensional experiments including heteronuclear correlation and double-quantum (DQ) MAS. Experiments probing internuclear dipolar couplings provide structural insight via identifying specific atomic proximities and determining specific distances and characterise dynamic processes via quantitative measurement of dipolar couplings.