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Journal ArticleDOI

A Raman and NMR study of KSbF6

01 Jan 1981-Journal of Physics and Chemistry of Solids (Pergamon)-Vol. 42, Iss: 6, pp 461-471
TL;DR: The 19 F spin-lattice relaxation results in the laboratory frame show that upon cooling from the tetragonal phase, KSbF 6 (I), the transition to the cubic phase occurs over a wide temperature range (~38 K) in which the two phases co-exist.
About: This article is published in Journal of Physics and Chemistry of Solids.The article was published on 1981-01-01. It has received 8 citations till now. The article focuses on the topics: Raman spectroscopy & Tetragonal crystal system.
Citations
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Journal ArticleDOI
TL;DR: In this article, solid polycrystalline KAsF6 and KSbF6 have been studied for both solution and solid-state NMR spectroscopy, and they have played an important role in the history of solution and NMR.
Abstract: Arsenic and antimony hexafluoride salts have played an important role in the history of both solution and solid-state NMR spectroscopy. Here, solid polycrystalline KAsF6 and KSbF6 have been studied...

9 citations

Journal ArticleDOI
TL;DR: In this paper, the polarized Raman spectra of single crystals of P42m-D symmetry were reported and the anions execute fourfold reorientational motions around the S4 axis of the crystals and an activation energy of 3.2 kcal mol−1 (13.4 kJmol−1) was calculated from the variation of the linewidths of Raman bands with temperature.
Abstract: The polarized Raman spectra of single crystals of KSbF6-I of P42m-D symmetry are reported. The predicted LO-TO splittings of the B2 and E modes were not observed and the vibrational spectra do not indicate a non-centrosymmetric structure. The calculated relative intensities of the Raman bands in the single-crystal spectra agree very well with the observed values. It is shown that the anions execute fourfold reorientational motions around the S4 axis of the crystals and an activation energy of 3.2 kcal mol−1 (13.4 kJ mol−1) is calculated from the variation of the linewidths of Raman bands with temperature. The barrier is penetrated by the anions and because of the jumping motions of the anions in KSbF6-I the small distortions from a centrosymmetric structure are averaged out and the Raman and infrared spectra appear to be mutually exclusive.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the physical properties of the low-temperature cubic phase f of polycrystalline samples of KSbF/sub 6 have been studied and a change in the temperature dependences of the quadrupole coupling constants at the /sup 121/Sb nuclei, the spin-lattice relaxation time T/sub 1/ for the 19/F nuclei and the dielectric constant epsilon(T) was given.
Abstract: The authors focus on the study of the physical properties of the low-temperature cubic phase f of KSbF/sub 6/. We give a change in the temperature dependences of the quadrupole coupling constants at the /sup 121/Sb nuclei, the spin-lattice relaxation time T/sub 1/ for the /sup 19/F nuclei, and the dielectric constant epsilon(T) in polycrystalline samples of KSbF/sub 6/. The NMR spectra of the /sup 121/Sb nuclei were recorded using a CW spectrometer at a frequency of 20 MHz. The T/sub 1/ measurements at the /sup 19/F nuclei were made using the IS-3 pulse spectrometer at a frequency of 27.2 MHz.

2 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the polarized Raman spectra of single crystals of rhombohedral CsSbF 6 belong to the space group R 3-C 2 3 i.

2 citations

References
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Book
01 Jan 1961

8,649 citations

Journal ArticleDOI
TL;DR: In this article, the second moment of the frequency deviation of the absorption line of the electron was calculated and the fourth moment was also computed to examine how good an approximation is the conventional assumption of a Gaussian shape.
Abstract: In regular crystals, the width of the absorption lines arising from the magnetic moment of the electron or nucleus is caused primarily by the interaction between the magnetic dipoles. It is prohibitively difficult to determine the precise shape of the absorption line theoretically, but the invariance of the diagonal sum in quantum mechanics permits the calculation of the second moment of the frequency deviation, and hence the r.m.s. line breadth. The latter agrees excellently with the observations of Pake and Purcell on the magnetic absorption of the F nucleus in Ca${\mathrm{F}}_{2}$, both in absolute magnitude, and in the dependence on the direction between the magnetic field and the principal cubic axes. The fourth moment was also computed to examine how good an approximation is the conventional assumption of a Gaussian shape. As long as no exchange is present (the nuclear case) the Gaussian model is moderately good. For the 100 direction in a cubic crystal, the theoretical ratio of root mean fourth to root mean square breadth is 1.25. Pake and Purcell's measurements yield 1.24. A Gaussian model would require 1.32. The theory is extended to include crystals with two kinds of spin moments (two types of nuclei, or simultaneous nuclear and electronic spin). Coupling between unlike moments is less effective (by a factor ⅔ in the r.m.s. width) than that between like in broadening the lines.In the paramagnetic absorption caused by electronic spin, it is imperative to include the effect of exchange coupling. This interaction does not contribute to the second moment, but greatly increases the fourth. As a result, the lines are peaked much more sharply than one would compute from the second moment with the Gaussian model for line shape. This "exchange narrowing" explains why microwave paramagnetic absorption lines are much narrower than one first conjectures from the amount of dipolar coupling.The theoretical calculations are given in Sections II-IV. The final sections V-VI give the comparison with the experiments of Pake and Purcell, and with the model of Bloembergen, Purcell, and Pound, for r-f absorption in liquids.

2,139 citations

Book
01 Jan 1971

1,027 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied reversible phase transformations of alkali sulphates, alkali nitrates, and various other inorganic substances by making use of differential thermal analysis and derived the strain energies associated with the transformations.
Abstract: Reversible phase transformations of alkali sulphates, alkali nitrates, and various other inorganic substances have been studied by making use of differential thermal analysis. Thermodynamic and kinetic data on the transformations have been obtained. Thermal hysteresis in reversible transformations has been examined, and the magnitude of hysteresis is shown to be related to the volume changes accompanying the transformations. The origin of hysteresis probably lies in the strain energies associated with the transformations. Approximate strain energies have been estimated from the analysis of the DTA data. On the basis of considerations from the theory of elasticity, it is possible to show that the strain energy is a function of ΔV. Thermodynamic considerations show that the strain energy is related to ΔT×ΔS.

92 citations

Book
01 Aug 1988
TL;DR: In this article, the problem of point defects in Ionic solids has been studied and theoretical calculations of the formation Energies of Schottky Defects have been carried out.
Abstract: 1. Lattice Dynamics.- Theory of Small Oscillations.- Effect of Lattice Symmetry.- Density of Vibrational States.- Vibrational Thermodynamic Properties of Crystals.- X-ray and Neutron Scattering.- 2. Cohesive Energies of Ionic Solids.- Born-Haber Cycle.- Born Treatment of Ionic Solids.- Some Related Aspects.- 3. Defect Chemistry and Non-Stoichiometric Compounds.- Point Defect Equilibria in Crystals.- The Systematica of Non-Stoichiometric Compounds.- Grossly Non-Stoichiometric Compounds.- Ferrous Oxide: A Case History.- Strong Defect Ordering: Intermediate Superstructure Phases.- Elimination of Defects: Crystallo graphic Shear.- Imperfections of Ordered Structures (Lattice Imaging).- Conclusions and Outstanding Problems.- 4. Theory of Point Defects in Ionic Crystals.- to Point Defects in Ionic Crystals.- Experimental Studies of Point Defects.- Theoretical Calculations of the Formation Energies of Schottky Defects.- Defect Interaction Energies.- Migration Energies.- Interstitial Defects.- Concluding Remarks.- 5. Dielectric Properties.- Definitions and Units.- Mechanisms of Polarization.- Alternating Current Phenomena.- Ferroelectrics.- 6. Magnetism.- Non-Interacting Atoms.- Magnetic Interactions.- Long-Range Order.- Spiral Configurations.- Magnetic Atoms in a Crystal.- Superexchange Interactions.- Collective d-Electron Model.- 7. Neutron Diffraction and Solid State Properties.- Thermal Neutrons.- Elastic Scattering.- Inelastic Scattering.- Conclusions.- 8. Magnetic Resonance.- Nuclear Moments end Nuclear Magnetic Resonance.- Spin-Lattice Relaxation.- Bloch Equations and Transverse Relaxation.- Experimental Arrangements.- NMR in Non-metallic Solids.- Quadrupolar Splittings in NMR.- NMR in Metals.- Chemical Shift and Spin Coupling in Solids.- Pure Quadrupole Resonance in Solids.- Electron Paramagnetic Resonance.- Concluding Remarks.- 9. Nuclear Magnetic Resonance in Superconductors and Dilute Alloys.- NMR in Superconductors.- NMR in Dilute Alloys.- 10. Magnetostriction in Materials.- Behaviour of Common Materials.- Conclusions.- 11. Mossbauer Effect and Dynamics of Atomic Motion in Solids.- Resonance Fluorescence.- Mossbauer's Experiment.- Resonance Absorption of Gamma Rays and Dynamics of Atomic Motion.- Experimental Results.- Concluding Remarks.- 12. Positron Annihilation in Solids.- Methods and Results.- 13. Elements of Order-Disorder Theory and Diverse Applications.- Statement of the Problem.- The Zero Order Approximation (Langmuir Isotherm).- The Fermi-Dirac Distribution Function.- Decomposition of the Lattice into Subfigures.- The Fowler-Guggenheim Adsorption Isotherm.- Thermodynamic Properties of Binary Mixtures in the Bragg-Williams Approximation.- 14. Diffusion in Solids.- The Diffusion Coefficient.- Intrinsic Diffusion Coefficients.- Self-Diffusion Coefficients.- Experimental Procedures.- 15. Ionic Conductivity.- Conduction Mechanisms in Ionic Crystals.- Anisotropy of Conduction in Ionic Crystals.- 16. Inorganic Glasses.- Constitution of Glass.- Glass formation.- Inorganic Glass Forming Systems.- Transport Properties of Glasses.- 17. Electrical Properties of Solid Catalysts.- Historical Introduction.- Classification of Solid Catalysts based on Electronic Properties.- Inverse Mixed Catalysts.- Conclusions.- 18. Dislocations and Solid State Reactions.- Dislocations, Their Structure and Properties.- The Role of Dislocations in Chemical Reactions.- 19. Solid State Reactions.- Role of Defects in the Reactivity of Solids.- Solid-Gas Reactions: Oxidation of Metals.- Solid-Solid Reactions.- Thermal Decomposition of Solids.- 20. Band and Transport Theories in Solids.- to Band Structure Concepts (Particle-in-the-Box).- Kronig-Penney Model.- Bloch Functions for the Circular Chain.- Band Structure for a Circular Chain in the Tight Binding Approximation.- Pauli Exclusion Principle and Fermi-Dirac Statistics.- Heat Capacity of a Metal.- Classification of Materials.- Elementary Discussion of Yarious Transport Phenomena.- Fermi Levels and Conductivity in Intrinsic and Extrinsic Semiconductors.- Transport Effects in Materials Characterized by 'Hopping' Electrons.- Brief Survey of Experimental Results.- 21. Spectroscopy of Metals and Semiconductors.- Macroscopic Theory and Experimental Methods.- Microscopic Theory of Optical Properties.- Optical Properties of Metals.- Optical Properties of Semiconductors.- Conclusions.- 22. Phase Transformations in Solids.- Thermodynamic Considerations.- Structural Changes in Transformations.- Kinetics of Transformations.- Order-Disorder Transitions.- Martensite Transformations.- Ferroelectric Transformations.- Magnetic Transitions.- Semiconductor-Metal Transitions.- High Pressure Transformations.- Born Treatment of Phase Transformations in Alkali Halides.- Comments on Experimental Techniques.

67 citations