Crystal structure of (Li{sub 0.5}K{sub 0.5}){sub 2}CO{sub 3} by neutron powder diffraction analysis

The modelling and/or describing of texture (i.e. preferred crystallographic orientation (PO)) is of critical importance in powder diffraction analysis - for structural study and phase composition. In the present study, the GSAS Rietveld refinement with generalized spherical harmonic (GSH) was used for describing isostatically-pressed molybdite powders neutron powder diffraction data collected in the ILL D1A instrument. The results showed that for texture in a single ND data of molybdite the reasonable crystal structure parameters may be obtained when applying corrections to intensities using the GSH description. Furthermore, the WIMV method was used to extract the texture description directly from a simultaneous refinement with 1368 whole neutron diffraction patterns taken from the sample held in a variety of orientations in the ILL D1B texture goniometer. The results provided a quantitative description of the texture refined simultaneously with the crystal structure. Finally, the (002) molybdite pole-figures were measured using the GKSS TEX2 texture goniometer. The results showed that neutron diffraction is an excellent tool to investigate the texture in molybdite.

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Neutron diffraction investigation of the temperature dependence of crystal structure and thermal motions of red HgI2

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768107043327 ◽

2007 ◽

Vol 63 (6) ◽

pp. 828-835 ◽

Cited By ~ 4

Author(s):

Dieter Schwarzenbach ◽

Henrik Birkedal ◽

Marc Hostettler ◽

Peter Fischer

Keyword(s):

Crystal Structure ◽

Neutron Diffraction ◽

Powder Diffraction ◽

Soft Mode ◽

Layer Structure ◽

Neutron Powder Diffraction ◽

Force Constants ◽

Quantum Oscillator ◽

Thermal Displacement ◽

Tetrahedral Layer

The structure of, and anisotropic thermal motions in, the red semiconductor tetrahedral layer structure of HgI2 have been studied with neutron powder diffraction as a function of temperature from 10 to 293 K. Average thermal displacement parameters U eq of the two atoms are comparable in size at 10 K, but U eq(Hg) increases considerably faster with temperature than U eq(I), the Hg—I bond being highly non-rigid. The anisotropic displacement tensor U (I) is strongly anisotropic with one term about twice as large as the others, while U (Hg) is nearly isotropic. All displacement tensor elements, except U 22(I), increase faster with temperature than harmonic quantum oscillator curves indicating a softening of the isolated-atom potentials at large amplitudes. A lattice dynamical model provides arguments that the anisotropic thermal motions of I are dominated by a soft mode with a wavevector at the [½ ½ 0] boundary of the Brillouin zone consisting essentially of coupled librations of the HgI4 tetrahedra, and by translations of the entire layer. The large vibration amplitudes of Hg suggest weak Hg–I force constants compared with the I–I force constants, allowing Hg to move quite freely inside the tetrahedra. The libration mode induces dynamic deformations of the Hg—I bond with twice its frequency. This provides a mechanism for the anharmonicity and may explain the lightening of the color from red to orange upon cooling at ca 80 K.

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Люминофоры холодного голубого излучения на основе оксида алюминия, допированного диспрозием

Физика твердого тела ◽

10.21883/ftt.2022.01.51837.196 ◽

2022 ◽

Vol 64 (1) ◽

pp. 95

Author(s):

И.В. Бакланова ◽

В.Н. Красильников ◽

А.П. Тютюнник ◽

Я.В. Бакланова

Keyword(s):

Crystal Structure ◽

Phase Composition ◽

Diffraction Analysis ◽

Powder Diffraction ◽

Thermal Quenching ◽

Emission Spectra ◽

X Ray ◽

White Emission ◽

Uv Excitation ◽

Quenching Of Luminescence

Al2О3:Dy3+ oxides with different colors luminescence were synthesized using precursor technology. The phase composition and crystal structure of the obtained materials were established by X-ray powder diffraction analysis. The excitation and emission spectra, decay curves, thermal quenching of luminescence were studied. Under UV excitation, the phosphors exhibit blue, purplish blue, white emission depending on the concentration of dysprosium and the temperature of annealing of the Al1-xDyx(OH)(HCOO)2 precursor in air.

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Resolution of the Crystal Structure of the Deficient Perovskite LaNiO2.5 from Neutron Powder Diffraction Data

Materials Science Forum ◽

10.4028/www.scientific.net/msf.228-231.747 ◽

1996 ◽

Vol 228-231 ◽

pp. 747-752

Author(s):

Julio A. Alonso ◽

M.J. Martínez-Lope

Keyword(s):

Crystal Structure ◽

Powder Diffraction ◽

Diffraction Data ◽

Neutron Powder Diffraction ◽

Powder Diffraction Data ◽

Neutron Powder Diffraction Data

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The Ab initio crystal structure determination of CuPt3O6 from a combination of synchrotron X-ray and neutron powder diffraction data

Journal of Physics and Chemistry of Solids ◽

10.1016/0022-3697(91)90203-c ◽

1991 ◽

Vol 52 (10) ◽

pp. 1273-1279 ◽

Cited By ~ 5

Author(s):

J.A. Hriljac ◽

J.B. Parise ◽

G.H. Kwei ◽

K.B. Schwartz

Keyword(s):

Crystal Structure ◽

Ab Initio ◽

Powder Diffraction ◽

Diffraction Data ◽

Structure Determination ◽

Neutron Powder Diffraction ◽

Powder Diffraction Data ◽

X Ray ◽

Neutron Powder Diffraction Data

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Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

Mineralogical Magazine ◽

10.1180/002646100549166 ◽

2000 ◽

Vol 64 (2) ◽

pp. 255-266 ◽

Cited By ~ 10

Author(s):

J. J. Reece ◽

S. A. T. Redfern ◽

M. D. Welch ◽

C. M. B. Henderson

Keyword(s):

Crystal Structure ◽

Phase Transition ◽

New York ◽

High Temperature ◽

Powder Diffraction ◽

Elevated Temperatures ◽

Neutron Powder Diffraction ◽

Site Preference ◽

A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

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