Impurity Effects on the Local Structure in the Mixed Hexachlorometallate (A2BCl6 : A = K, Rb, B = Sn, Re, and Pb) Studied by the Chlorine NQR

Chlorine NQR was studied for the isostructural hexachlorometallate mixed system. The study shows that Isomorphic hexachlorometallate solid solutions exhibit often impurity induced local structural order because of their relatively clear local site symmetry. This is manifested in the formation of a few satellite lines near the original resonance line and results from the random distribution of impurities on the lattice sites of the corresponding counterpart ions. Using the point charge model and a simple binomial function for the occupation probability of the guest ions on the host lattice sites, the position and the line intensity could be determined, the results of which are in good agreement with the NQR-observation. The temperature region of lattice dynamics in the crystal seems to shift in proportion to the impurity content. This fact explains the gradual change of the transition temperature in the mixed crystal between two starting materials.

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Rare Earth Doped Lanthanum Calcium Borate Polycrystalline Red Phosphors

Advances in Materials Science and Engineering ◽

10.1155/2014/819057 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

H. H. Xiong ◽

C. Zhu ◽

X. Zhao ◽

Z. Q. Wang ◽

H. Lin

Keyword(s):

Rare Earth ◽

Light Emitting Diode ◽

Solid State Reaction Method ◽

Host Lattice ◽

Site Symmetry ◽

Calcium Borate ◽

Light Emitting ◽

Red Phosphors ◽

Local Site ◽

White Light Emitting Diodes

Single-phased Sm3+doped lanthanum calcium borate (SmxLa2−xCaB10O19, SLCB,x=0.06) polycrystalline red phosphor was prepared by solid-state reaction method. The phosphor has two main excitation peaks located at 398.5 nm and 469.0 nm, which are nicely in accordance with the emitting wavelengths of commercial near-UV and blue light emitting diode chips. Under the excitation of 398.0 nm, the dominant red emission of Sm3+in SLCB phosphor is centered at 598.0 nm corresponding to the transition of4G5/2 → 6H7/2. The Eu3+fluorescence in the red spectral region is applied as a spectroscopic probe to reveal the local site symmetry in the host lattice and, hence, Judd-Ofelt parametersΩt (t=2, 4)of Eu3+in the phosphor matrix are derived to be3.62×10-20and1.97×10-20 cm2, indicating a high asymmetrical and strong covalent environment around rare earth luminescence centers. Herein, the red phosphors are promising good candidates employed in white light emitting diodes (LEDs) illumination.

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Data-model Comparison for the mid-Pliocene Warm Period

10.5194/egusphere-egu21-4802 ◽

2021 ◽

Author(s):

Julia Tindall ◽

Alan Haywood ◽

Ulrich Salzmann ◽

Aisling Dolan

Keyword(s):

Data Model ◽

Model Comparison ◽

Surface Air Temperature ◽

High Latitudes ◽

Orbital Forcing ◽

Local Site ◽

Modern Analogue ◽

Intercomparison Project ◽

Global Mean ◽

Good Agreement

Modelling results from PlioMIP2 (the Pliocene Model Intercomparison Project Phase 2) focussing on MIS KM5c; ~3.205Ma, suggest that global mean surface air temperature was 1.7 &#8211; 5.2 &#176;C higher than the preindustrial.&#160; This warming was amplified at the poles and over land.&#160; The results are in reasonable agreement with paleodata over the ocean.&#160; &#160;Over the land the situation is more complicated.&#160; Model and data are in very good agreement at lower latitudes, however at high latitudes an initial data-model comparison shows much warmer mPWP temperatures from data than from models.&#160; &#160;Here we consider possible reasons for this data-model discord at high latitudes.&#160; These include uncertainties in model boundary conditions (such as CO2 and orbital forcing), and whether there are local site-specific conditions which need to be accounted for.&#160; We also show that the seasonal cycle in mPWP temperatures at these high latitude sites has no modern analogue.&#160; This could lead to inaccuracies when comparing model derived mean annual temperatures with quantitative climatic estimates from palaeobotanical data using Nearest Living Relative methods.

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Single oxygen vacancy in BaCoO3: Hybrid DFT calculations and local site symmetry approach

Solid State Ionics ◽

10.1016/j.ssi.2021.115835 ◽

2022 ◽

Vol 375 ◽

pp. 115835

Author(s):

Davis Zavickis ◽

Guntars Zvejnieks ◽

Andrei Chesnokov ◽

Denis Gryaznov

Keyword(s):

Oxygen Vacancy ◽

Dft Calculations ◽

Site Symmetry ◽

Symmetry Approach ◽

Local Site ◽

Single Oxygen

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Luminescence of Eu3+ as a probe for the determination of the local site symmetry in β-Ca3(PO4)2-related structures

CrystEngComm ◽

10.1039/c9ce00931k ◽

2019 ◽

Vol 21 (35) ◽

pp. 5235-5242 ◽

Cited By ~ 8

Author(s):

Dina V. Deyneko ◽

Ivan V. Nikiforov ◽

Dmitry A. Spassky ◽

Yuri Yu. Dikhtyar ◽

Sergey M. Aksenov ◽

...

Keyword(s):

Dielectric Spectroscopy ◽

Site Symmetry ◽

X Ray Diffraction ◽

X Ray ◽

Local Site ◽

Sensitive Determination

The study reveals opportunity of using the emission of Eu3+, together with X-ray diffraction, and dielectric spectroscopy, for sensitive determination of the symmetry β-TCP related structures.

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Assessing the Instantaneous Stiffness of Cracked Reinforced Concrete Beams Based on a Gradual Change in Strain Distributions

Advances in Materials Science and Engineering ◽

10.1155/2020/7453619 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Chunyu Fu ◽

Dawei Tong ◽

Yuyang Wang

Keyword(s):

Experimental Data ◽

Reinforced Concrete ◽

Cross Section ◽

Concrete Beams ◽

Internal Force ◽

Experimental Results ◽

Reinforced Concrete Beams ◽

Gradual Change ◽

Concrete Cracking ◽

Good Agreement

Concrete cracking causes a gradual change in strain distributions along the cross section height of reinforced concrete beams, which will finally affect their instantaneous stiffness. A method for assessing the stiffness is proposed based on the gradual change, which is considered through modeling different strain distributions for key sections in cracked regions. Internal force equilibria are adopted to find a solution to top strains and neutral axes in the models, and then the inertias of the key sections are calculated to assess the beam stiffness. The proposed method has been validated using experimental results obtained from tests on five reinforced concrete beams. The predicted stiffness and displacements are shown to provide a good agreement with experimental data. The instantaneous stiffness is proven to greatly depend on the crack number and depth. This dependence can be exactly reflected by the proposed method through simulating the gradual change in concrete strain distributions.

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Identification of Transition Metal Sites in Fused SiO2 by X-Ray Absorption Spectroscopy

MRS Proceedings ◽

10.1557/proc-61-259 ◽

1985 ◽

Vol 61 ◽

Cited By ~ 2

Author(s):

Farrel W. Lytle ◽

Robert B. Greegor

Keyword(s):

Transition Metal ◽

Transition Metals ◽

Absorption Spectroscopy ◽

Optical Data ◽

Site Symmetry ◽

X Ray ◽

Hydrolysis Method ◽

Fused Quartz ◽

X Ray Absorption ◽

Good Agreement

ABSTRACTX-ray absorption spectroscopy is used to determine valence and site symmetry for all the 3d transition metals in fused quartz prepared by the flame hydrolysis method. The results are compared with optical data on the same samples with generally good agreement.

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Local site symmetry and electronic structure of trialuminide and related intermetallic alloys probed by solid-state NMR

Physical Review B ◽

10.1103/physrevb.58.2988 ◽

1998 ◽

Vol 58 (6) ◽

pp. 2988-2997 ◽

Cited By ~ 40

Author(s):

T. J. Bastow ◽

C. T. Forwood ◽

M. A. Gibson ◽

M. E. Smith

Keyword(s):

Electronic Structure ◽

Solid State ◽

Solid State Nmr ◽

Site Symmetry ◽

Intermetallic Alloys ◽

Local Site

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Divergent-beam X-ray photography of crystals

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1947.0002 ◽

1947 ◽

Vol 240 (817) ◽

pp. 219-250 ◽

Cited By ~ 118

Keyword(s):

Wave Length ◽

Impurity Content ◽

Type I ◽

X Rays ◽

Divergent Beam ◽

X Ray ◽

Air Temperatures ◽

High Degree ◽

Good Agreement

Divergent-beam X-ray photography of single crystals by transmission can be used to study the ‘extinction’, that is, the diminution of the transmitted radiation that takes place at the Bragg reflexion angles. The intensity and geometry of the absorption lines observed give useful information about the texture of the crystal. Divergent beam photographs have shown that many crystals of organic compounds are unexpectedly perfect, and that sudden cooling to liquid-air temperatures will increase the mosaic character of their structure by an important factor and make them more suitable for structural analysis by the usual methods. Type I diamonds, and natural ice even near to its melting-point, are also found to possess a high degree of perfection, which cannot be removed by liquid-air treatment. The divergent beam method may be used for the determination of orientation, but it is important that the wave-length of X-rays employed should be correctly related to the size and nature of the crystal. In certain favourable cases it is possible to make precision measurements of lattice constant or of wave-length from divergent beam photographs, without the use of any kind of precision apparatus. By such means it has been shown that the C—C distance in individual diamonds varies from 1541.53(± 0-02) to 1541.27X, (1.54465-1-54440A), a difference presumably due to varying impurity content. Using diamond and a brass anticathode, the Zn Ka 1 wave-length, relative to Cu K Ka 1 as 1537.40X, is found to be 1432.21 ( ± 0-04) X. Temperature control would improve the accuracy of this measurement, which is, however, in good agreement with the latest value obtained by orthodox precision methods.

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