Showing papers on "Crystal published in 1980"
TL;DR: In this article, the attachment energy Eatt, defined as the energy per molecule released when one slice of thickness dckl crystallizes onto a crystal face (hkl), was investigated and it was shown that the relative growth rate R of a face always increases with increasing Eatt.
630 citations
TL;DR: In this paper, X-ray powder diffraction is used to identify the strong superlattice reflections associated with the ordering of scandium and tantalum ions in the B-site, and to demonstrate quantitatively how the degree of ordering can be modified by suitable thermal treatment.
Abstract: Simple crystal-chemical arguments were used to suggest that in the ferroelectric perovskite lead-scanium-tantalate (PbSc0.5Ta0.5O3) the B-site cations in this simple ABO3 structure should be close to the boundary between order and disorder. Both polycrystal ceramic and single crystal materials of this composition have been grown. In this study X-ray powder diffraction is used to identify the strong superlattice reflections associated with the ordering of scandium and tantalum ions in the B-site, and to demonstrate quantitatively how the degree of ordering can be modified by suitable thermal treatment. Thermal changes associated with the ferroelectric Curie temperature have been measured by differential scanning calorimetry and show very clearly the manner in which the diffuse (broadened) transition in this crystal is sharpened by increase in the B-cation ordering.
410 citations
TL;DR: Sherwood as mentioned in this paper describes the phenomenon that crystals made of essentially spherical molecules undergo several phase transitions as the temperature is raised towards the melting point, and the higher temperature phases are usually orientationally disordered and the 'crystal' tends to be readily deformable, often merely under gravity.
Abstract: J N Sherwood (ed) 1979 Chichester: John Wiley xxvi + 383 pp price £19.50 It is a common phenomenon that crystals made of essentially spherical molecules, e.g. CCI4, undergo several phase transitions as the temperature is raised towards the melting point. The higher temperature phases are usually orientationally disordered and the 'crystal' tends to be readily deformable, often merely under gravity.
335 citations
TL;DR: Matrix protein, a pore-forming transmembrane protein spanning the outer membrane of Escherichia coli, has been obtained in a variety of three- dimensional crystal forms amenable to both electron microscope and x- ray analyses.
Abstract: Matrix protein, a pore-forming transmembrane protein spanning the outer membrane of Escherichia coli, has been obtained in a variety of three-dimensional crystal forms amenable to both electron microscope and x-ray analyses. Successful association into large crystals depended on the use of alpha-octyl glucoside, a detergent with relatively low affinity for the protein. Electron micrographs of thin-sectioned crystals show a high degree of order. Preliminary crystallographic data suggest that the crystals, which exhibit diffraction to 3.8 A, have a cubic space group.
246 citations
TL;DR: In this article, the mechanism for crystal transformation in poly(vinylidene fluoride) by a tensile deformation at atmospheric pressure was investigated in the temperature range 25-150 °C.
181 citations
Journal Article•
TL;DR: In this article, the early 1950s adoption of the X-ray powder diffractometer for clay studies helped to solve some of the problems in charactetization in nomenclature.
Abstract: Because of their small particle sizes and v~riable degrees of crystal perfection, it is not surprisi4g that clay minerals proved extremely difficult to characterize adequately prior to the development of ~odem analytical techniques. Problems in charactetization led quite naturally to problems in nomenclatute, undoubtedly more so than for the macroscopic~ more crystalline minerals. The popular adoption ~ the early 1950s of the X-ray powder diffractometer for clay studies helped to solve some of the probl
176 citations
TL;DR: With use of bromine atoms, deposited on the surface of a silicon single crystal, the presence of x-ray standing waves above the crystal surface has been detected under conditions of strong Bragg diffraction.
Abstract: With use of bromine atoms, deposited on the surface of a silicon single crystal, the presence of x-ray standing waves above the crystal surface has been detected under conditions of strong Bragg diffraction.
172 citations
TL;DR: In this article, the effects of temperature-gradient metamorphism on the shape of depth-hoar crystals were quantified with a view to quantifying the effect of the main parameters of temperature gradients on crystal growth.
Abstract: The present study was carried out with a view to quantifying the effects of the main parameters ot temperature-gradient metamorphism. Cold-room simulation tests showed crystal growth to be an increasing function of the temperature-gradient modulus with a lower limit of around 0.25 deg/cm. This growth also proved to be a function of temperature itself reaching a maximum at around –5°C Furthermore the shape of depth-hoar crystals was also shown to depend on temperature and to resemble approximately that obtained when crystals are formed in the atmosphere. Temperature-gradient metamorphism is observed to take place at constant density. Increase in crystal size is a decreasing function of density with a lower limit of around 150 kg/m3, below which destructive metamorphism occurs accompanied by packing (similar to ET metamorphism): the upper limit is situated at approximately 350 kg/m3 and no depth-hoar crystals occur above this value. The series of Cold-room simulations enabled a highly simplified model of crystal growth to be constructed.
157 citations
01 Jan 1980
TL;DR: In this article, the authors present an experimental evidence for Quadrupolar interactions in Cubic Rare-Earth Compounds (CRSC) in CEF Split Systems (CSEF split systems).
Abstract: Section 1: Crystal Field and Structural Effects.- Symmetry and Experiment in Magnetism (Invited).- Structural Phase Transitions and Magnetostriction in Metallic Rare-Earth Compounds (Invited).- Pressure Effects and Lattice Parameter Correlations in CEF Split Systems (Invited).- Random Crystal Field Effects in Amorphous Rare-Earth Alloys (Invited).- Section 2: Lattice Effects I.- Low Frequency Dynamics in Concentrated 4f CEF Systems (Invited).- Interactions of Rare-Earth Ions with Phonons (Invited).- New Experimental Evidence for Quadrupolar Interactions in Cubic Rare-Earth Compounds (Invited).- Magnetic Anisotropy and Spin Reorientations in HoxTb1-xFe2, DyxTb1-xFe2 and HoxTbyDy1-x-y Fe2.- Thermal Expansion and Magnetostriction of Mg Single Crystals with Heavy Rare Earth Impurities.- Elastic Moduli of Amorphous Rare-Earth Alloys.- Magnetostriction of Dilute Tb Ions in Several Metallic Matrices.- First Order Transitions and the Magnetic Phase Diagram of CeSb.- Origin of Crystal Field and Magnetoelasticity in Rare Earth Intermetallic Compounds.- Terbium3+ Coupling Parameters and the Phase Diagram of the Singlet Ground State Terbium Monopnictides.- Section 3: Lattice Effects II.- Exchange and Crystal Field Excitations in Rare-Earth Iron and Rare Earth Cobalt Laves-Phase Compounds (Invited).- Soft Modes and Mode Splitting in Paramagnetic TbP (Invited).- Theory of Static and Dynamic Properties of Crystal Field Systems Including Correlation Effects (Invited).- Pressure Effects on the Crystal Field in Rare Earth Chalcogenides and Pnictides.- Excitation Spectrum of Van Vleck Magnets.- H3+ - A Basis for Clustering in Metallic Hydrides.- Determination of Crystal Fields Combining Paramagnetic Anisotropy and Neutron Scattering.- Rare Earth-Iron Exchange Interaction and Crystal Field-Like Terms in Garnets.- Investigation of Crystal Field in PrNi5.- Section 4: Actinides.- Actinide 5f Systems: Experimental Determination of the Magnetic Response Function (Invited).- Neutron Scattering Studies of Uranium Compounds (Invited).- Sources of Anisotropy and Extraordinary Magnetic Ordering in Cerium and Actinide Intermetallics (Invited).- Dispersion of Collective Magnetic Excitons in a Single Crystal of the Actinide Intermetallic UPd3 (Invited).- The Magnetic Susceptibility of 249Bk Metal.- Ordered Quadrupolar State with a Nearly Zero Magnetic Moment in NpO2.- Is the Intermediate Valence State Possible in the Uranium Tellurides?.- Crystal Field Effects in Some Ionic Uranium Compounds.- Transport Properties, Lattice Constants, Susceptibility and Specific Heat of UPd3.- Section 5: Kondo and Intermediate Valence Properties.- Energy Parameters and Crystal Field Effects in the Mixed Valence Problem: Chemically Collapsed Cerium (Invited).- Valence Instabilities as a Source of Actinide System Inconsistencies.- Thermal Properties of Exotic Cerium Compounds.- A Novel Low Temperature Phase Transition in Mixed Valent Sm4Bi3.- Mixed Valence, Crystalline Electric Fields and the Kondo Effect in Ce (Pd,Ag)3.- Low Temperature Properties of (La1-xSmx) Sn3 and CeSn3.- Ground State and Magnetic Responses of Model Valence-Fluctuation Systems.- Section 6: Transport and Thermodynamic Properties.- Multipolar f Electron-Conduction Band Interactions in Rare Earth Compounds (Invited).- Electrical Resistivity Investigations on Metallic Rare Earths (Invited).- Magneto-Transport in F-Electron Systems-Quadrupolar and Orbital Exchange Effects (Invited).- Electrical Resistivity in Pr3T1-an Induced Moment Ferromagnet Near Threshold.- Antiferromagnetic Ordering in ErCu: Resistivity and Specific Heat.- Electrical and Thermal Properties of Magnetically Ordered Metallic Compounds TbZn, TbGd, GdCd.- Kondo Effect in the Presence of Crystalline Electric Fields - Ce (In, Sn)3.- Section 7: Singlet Ground State and Other Properties.- Series Expansion for CEF Split Systems (Invited).- Theory of Singlet-Ground-State Ferromagnetism in Pr3Se4: A Cubic System with Low Local Symmetry.- Van Vleck Orbit-Lattice Interactions in LaZ (Z=P, As, Sb, Bi).- Theory of g-shift and Linewidth in CeP Excited State EPR.- REA12's: A Real and Yet Unresolved Problem.- Electric Field Gradient (Crystal Field) in Amorphous f-Electron Systems.- Magnetic Excitations in Holmium Phosphide.- A General Method for Determining Crystal Field Effects on Magnetic Ions.- Determination of Crystal Field Parameters in ErBe13 by Inelastic Neutron Scattering.- Section 8: Superconductivity.- The Influence of Crystalline Electric Fields on the Superconducting Properties of Rare Earth Alloys and Compounds (Invited).- Superconductivity, Long-Range Magnetic Order, and Crystal Field Effects in RERh4B4 Compounds (Invited).- Crystal Field Effects in Magnetic Superconductors (Invited).- Roles of Crystal Fields in Magnetic Superconducting Rare-Earth Rhodium Borides (Invited).- Crystalline Electric Field Manifestations in Tunneling into Superconductors.- Crystal Field Effects in the Magnetic Susceptibility of Dilute Alloys of LaSn3 Containing Nd Impurities.- Section 9: Lifetime Effects.- Neutron Studies of CEF Excitations and Linewidths of Dilute Systems (Invited).- Linewidth of Quasi-Elastic and Inelastic Crystal Field Excitations in CeAg and CeMg Compounds (Invited).- List of Participants.- Material Index.
154 citations
TL;DR: In this paper, the diffusion of indium in GaSb was investigated in both Ga-saturated and Sb-Saturated crystals for temperatures ranging from 520°C to the melting point (712°C).
Abstract: Diffusion of indium in GaSb is investigated in both Ga-saturated and Sb-saturated crystals for temperatures ranging from 520°C to the melting point (712°C). It is found that the composition of the crystal does have an influence on the diffusion coefficient: indium diffuses faster in Sb-rich than in Ga-rich crystals. The temperature dependence of the diffusion coefficient resembles that of the antimony partial pressure over the compound. This leads us to conclude that indium diffuses by a vacancy mechanism on the gallium sublattice. The results are analysed in terms of a defect-structure model for GaSb.
152 citations
TL;DR: The results of scattering experiments revealing this phenomenon are surveyed in detail, and are used in an assessment of current theories, subdivided into three categories: those which seek to describe the phenomenon within an extended phonon-based theory; those which attempt to trace the effect to the formation of long-lived clusters of precursor order; and those which associate the quasi-elastic scattering with crystal imperfections as mentioned in this paper.
Abstract: The dynamical behaviour of systems exhibiting structural phase transitions is reviewed, with particular emphasis on the problems posed by the simultaneous existence of quasi-elastic and phonon features in the dynamic response of the soft coordinates. The results of scattering experiments revealing this phenomenon are surveyed in detail, and are used in an assessment of current theories, subdivided into three categories: those which seek to describe the phenomenon within an extended phonon-based theory; those which attempt to trace the effect to the formation of long-lived clusters of precursor order; and those which associate the quasi-elastic scattering with crystal imperfections.
TL;DR: In this article, the concentrostatic twin-electrode thin-layer (TTL) technique has been used to obtain thermodynamic data on the lead ion adsorption on poly- and monocrystalline gold substrates in perchlorate solution.
TL;DR: Dynamic models of crystal surfaces have provided new insights into the crystal growth process and certain impurities have been found to cause a larger increase in the growth rate than screw dislocations.
Abstract: Dynamic models of crystal surfaces have provided new insights into the crystal growth process. The effects of surface roughening, dislocations, and impurities have been assessed. Certain impurities have been found to cause a larger increase in the growth rate than screw dislocations.
TL;DR: In this article, the fundamental phenomenon of the interaction between a solute or suspended particle and an ice-water interface during freezing is described extensively, revealing the fact that particles of different kinds, sizes and shapes interact in different ways with the solid-liquid interface.
IBM1
TL;DR: In this article, it is demonstrated that one can distinguish between a supercooled liquid that becomes a glass and a super-cooling liquid that nucleates to a defect crystal during a quench using the isothermal-isobaric Monte Carlo method.
Abstract: It is demonstrated that one can easily distinguish between a supercooled liquid that becomes a glass and a supercooled liquid that nucleates to a defect crystal during a quench using the isothermal–isobaric Monte Carlo method.(AIP)
TL;DR: In this paper, the Czochralski-grown ZnWO4 single crystal was studied and the total luminescence output under x-ray excitation was found to be 2.3 times larger than that of the best Bi4Ge3O12 at room temperature with small afterglow.
Abstract: Scintillation characteristics of the Czochralski‐grown ZnWO4 single crystal were studied. This crystal, with light red‐brown color, exhibits a maximum luminescence wavelength of 480 nm under excitation at 254 nm. The total luminescence output under x‐ray excitation at 254 nm. The total luminescence output under x‐ray excitation was found to be 2.3 times larger than that of the best Bi4Ge3O12 at room temperature with small afterglow.
TL;DR: In this paper, the vibrational spectrum of hydrogen and deuterium atoms adsorbed on the surface of a graphite single crystal by means of atomic beam scattering in UHV conditions was investigated.
Abstract: We have investigated the vibrational spectrum of hydrogen and deuterium atoms adsorbed on the (0001) surface of a graphite single crystal by means of atomic beam scattering in UHV conditions. Bound state resonances, which appear as minima in the specularly reflected beam have been detected over a wide range of incidence and azimuthal angles. Energy levels at 31.6±0.2 and 15.3±0.3 meV for 1H and at 35.4 ±2; 21.35±0.1; 12.0±0.1, and 5.9±0.3 meV for 2H have been determined. By fitting the experimental energy levels to those calculated with the potential the following values of the parameters are obtained: D=43.3±0.5 meV; λ=1.36±0.03 A−1; p=4.4±0.6. The hypothesis that the interaction potential is the sum over all crystal layers of an atom–single layer potential V*(z) is used. V*(z) has a well depth D*=39.2±0.5 meV and a long range behavior given by C*4/z4 with C*4=5.2±0.3 eV A4.
Journal Article•
TL;DR: Li 2 B 4 O 7 : Cu crystal phosphor prepared by a sintering method was found to have the most promising characteristics for use as TLD, i.e., a TL emission band at 368 nm and a moisture resistant property.
TL;DR: In this paper, the authors determined the partitioning of major and minor elements between augite and melt as a function of cooling rate for two high-titanium basalt compositions.
Journal Article•
TL;DR: In this article, the effect of high-dose radiation on the paraffinoid crystal lattice is investigated. But the main finding is not the occurrence of an orthorhombic-hexagonal phase transition on heating subsequent to irradiation at ambient temperature beyond a certain critical dose.
TL;DR: In this article, the atomic coordinates and the anisotropic thermal parameters of CsH 2 PO 4 crystal in the paraelectric phase were obtained using three-dimensional X-ray intensity data collected by a four-circle automatic diffractometer at room temperature.
Abstract: The atomic coordinates and the anisotropic thermal parameters of CsH 2 PO 4 crystal in the paraelectric phase have been obtained using three-dimensional X-ray intensity data collected by a four-circle automatic diffractometer at room temperature. The structure is refined to R =0.029 for 780 independent reflections. Two types of hydrogen bonds are clearly distinguished in the electron density maps which display distributions corresponding to order and disorder of protons, respectively.
TL;DR: In this article, an experimental study has been carried out by using a constant volume variable pressure system and the uptake curves have been analyzed by solution of the appropriate diffusion equation on the assumption that the uptake rate obtained is limited by intracrystalline diffusion.
Abstract: Starting from the necessity for more substantial evidence with regard to the occurrence of intracrystalline diffusion as the rate-limiting transport mechanism in sorption processes on zeolites, the variation of zeolite crystal size is regarded as a criterion and used in the case of the sorption system n-hexane/MgA zeolite.The experimental study has been carried out by using a constant volume variable pressure system. The uptake curves have been analysed by solution of the appropriate diffusion equation on the assumption that the uptake rate obtained is limited by intracrystalline diffusion. An additional analysis was done considering the sorption process as being limited by surmounting a transport resistance in the surface region of zeolite crystals.The experimental parameters covered the following ranges: temperature: 373–623 K, pressure: ≈ 4 × 10–3–265 Pa, amount sorbed: ≈ 2 × 10–4–3 × 10–1 mmol g–1, crystal size (mean edge length of cubic crystals): 0.7–43 µm.Over the whole of the ranges of amount sorbed and crystal size the apparent diffusion coefficient is independent of amount sorbed at constant temperature. At each temperature an unambiguous dependence of the apparent diffusion coefficient on zeolite crystal size has been found.Taking into account the analysis of sorption kinetics by a surface barrier model, the shape of uptake curves, the values of the apparent energy of activation and the peculiarities of crystal habit of several sample sizes the following conclusions concerning the rate-limiting transport mechanisms can be drawn: (i) In the crystal size region 0.7–13 µm a surface barrier is possible (for several crystal samples a surface barrier dependent on the crystal size is probable at lower temperatures). (ii) In the case of zeolite crystals with the sizes 33–43 µm the uptake process seems to be limited by intracrystalline diffusion.The energy of activation assumes values of ≳ 50 kJ mol–1 and ≈ 42 kJ mol–1 for the cases (i) and (ii), respectively.
TL;DR: In this article, a review of experimental studies in ultra high vacuum systems mostly concerns ellipsometric measurements of chemisorption of oxygen on metal surfaces (Ag, Cu, Ni).
TL;DR: The distribution of interatomic distances in amorphous NaAlSi3O8 has been determined at 805°C by X-ray radial distribution analysis to investigate structural differences between the glass (T < 763°C) and the supercooled liquid (763°C < T < 1118°C). Except for slight differences attributable to thermal expansion, no significant changes were observed as mentioned in this paper.