Comparative analysis of the difference of local structure between EPR theory and X-ray diffraction experiment for NiSiF6·6H2O crystal

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

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Structure Evolution of Au50Cu50 Alloy from Melt to the Disordered Solid Solution

Materials Science Forum ◽

10.4028/www.scientific.net/msf.993.273 ◽

2020 ◽

Vol 993 ◽

pp. 273-280

Author(s):

Yan Wen Bai ◽

Xiao Lin Zhao ◽

Xiu Fang Bian ◽

Kai Kai Song ◽

Yan Zhao

Keyword(s):

Solid Solution ◽

Monte Carlo ◽

Local Structure ◽

Solution Structure ◽

Liquid Structure ◽

Structure Evolution ◽

Reverse Monte Carlo ◽

Diffraction Experiment ◽

X Ray Diffraction ◽

X Ray

The liquid local structure of Au50Cu50 solid solution was detected by high-temperature X-ray diffraction experiment and Reverse Monte Carlo (RMC) simulation. The clusters in the liquid Au50Cu50 alloy comprise the 12-coordinated polyhedron with Au center, which was the same as the clusters in the liquid pure Au. In the case of alloying, there was a high population of Au-Au bonds, and the local structure around Cu atoms was changed. In the case of solidification, the 12-coordinated clusters around Au atoms were preserved into the AuCu alloy, forming the disordered solid solution structure. The strong tendency for Cu-Cu bonds was weakened from 2.35 Å in the liquid to 2.81 Å in the solid solution, and the local structure around Cu atoms rearranges. It is shown that the liquid structure of the Au50Cu50 alloy plays a crucial role in the solid solution. Our findings elucidate that the disordered solid solution structure in AuCu alloy stems from the highly dominated 12-coordinated clusters associated with centered Au atom in the melt.

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Antiphase Boundaries in Ordered Ni3FE Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006221x ◽

1969 ◽

Vol 27 ◽

pp. 62-63

Author(s):

Y. H. Liu

Keyword(s):

Domain Size ◽

Antiphase Domain ◽

X Ray Diffraction ◽

X Ray ◽

Hardening Mechanism ◽

Superlattice Structure ◽

Disordered Phase ◽

Domain Boundaries ◽

Atomic Scattering ◽

The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

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X-ray microprobe for materials science

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168013 ◽

1994 ◽

Vol 52 ◽

pp. 56-57

Author(s):

G.E. Ice

Keyword(s):

Crystallographic Orientation ◽

Local Structure ◽

Materials Science ◽

Chemical Information ◽

X Ray Diffraction ◽

Ray Optics ◽

X Ray ◽

Novel Materials ◽

New Information ◽

Elemental Sensitivity

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E≥5 keV) microprobes. With new x-ray optics these microprobes can achieve micron and submicron spatial resolutions. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature will have important applications to materials science. For example, x-ray fluorescent microanalysis of materials can reveal elemental distributions with greater sensitivity than alternative nondestructive probes. In materials, segregation and nonuniform distributions are the rule rather than the exception. Common interfaces to whichsegregation occurs are surfaces, grain and precipitate boundaries, dislocations, and surfaces formed by defects such as vacancy and interstitial configurations. In addition to chemical information, an x-ray diffraction microprobe can reveal the local structure of a material by detecting its phase, crystallographic orientation and strain.Demonstration experiments have already exploited the penetrating nature of an x-ray microprobe and its inherent elemental sensitivity to provide new information about elemental distributions in novel materials.

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Study of superficial stress gradients by computer simulation and x-ray diffraction experiment

10.1117/12.836980 ◽

2008 ◽

Author(s):

Joaquim T. Assis ◽

Vladimir I. Monin ◽

Susana M. Iglesias

Keyword(s):

Computer Simulation ◽

Diffraction Experiment ◽

X Ray Diffraction ◽

X Ray ◽

Stress Gradients

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Silicate-germanate K2Y[(Si3Ge)O10(OH)] with unusual complex corrugated layer and its correlation to ring silicate gerenite and chain silicate chkalovite

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2020-0005 ◽

2020 ◽

Vol 235 (4-5) ◽

pp. 167-172

Author(s):

Anastasiia P. Topnikova ◽

Elena L. Belokoneva ◽

Olga V. Dimitrova ◽

Anatoly S. Volkov ◽

Leokadiya V. Zorina

Keyword(s):

Low Temperature ◽

Cross Section ◽

Complex Anion ◽

Diffraction Experiment ◽

X Ray Diffraction ◽

Unit Cell Parameters ◽

X Ray ◽

Cell Parameters ◽

Chain Silicate ◽

Novel Complex

AbstractA new silicate-germanate K2Y[(Si3Ge)O10(OH)] was synthesized hydrothermally in a system Y2O3:GeO2:SiO2 = 1:1:2 (T = 280 °C; P = 90–100 atm.); K2CO3 was added to the solution as a mineralizer. Single-crystal X-ray diffraction experiment was carried out at low temperature (150 K). The unit cell parameters are a = 10.4975(4), b = 6.9567(2), c = 15.4001(6) Å, β = 104.894(4)°; V = 1086.86(7) Å3; space group is P 21/c. A novel complex anion is presented by corrugated (Si,Ge) tetrahedral layers connected by couples of YO6 octahedra into the mixed microporous framework with the channels along b and a axes, the maximal size of cross-section is ~5.6 Å. This structure has similarity with the two minerals: ring silicate gerenite (Ca,Na)2(Y,REE)3Si6O18 · 2H2O and chain silicate chkalovite Na2BeSi2O6. Six-member rings with 1̅ symmetry as in gerenite are distinguished in the new layer. They are mutually perpendicular to each other and connected by additional tetrahedra. Straight crossing chains in chkalovite change to zigzag four-link chains in the new silicate-germanate layer.

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Problems Associated with Kα Doublet in Residual Stress Measurements

Advances in X-ray Analysis ◽

10.1154/s0376030800006492 ◽

1979 ◽

Vol 23 ◽

pp. 333-339

Author(s):

S. K. Gupta ◽

B. D. Cullity

Keyword(s):

Residual Stress ◽

Silicon Powder ◽

Lattice Parameter ◽

Diffraction Peak ◽

Parameter Determination ◽

X Ray Diffraction ◽

X Ray ◽

Analysis Techniques ◽

The Difference ◽

Similar Accuracy

Since the measurement of residual stress by X-ray diffraction techniques is dependent on the difference in angle of a diffraction peak maximum when the sample is examined consecutively with its surface at two different angles to the diffracting planes, it is important that these diffraction angles be obtained precisely, preferably with an accuracy of ± 0.01 deg. 2θ. Similar accuracy is desired in precise lattice parameter determination. In such measurements, it is imperative that the diffractometer be well-aligned. It is in the context of diffractometer alignment with the aid of a silicon powder standard free of residual stress that the diffraction peak analysis techniques described here have been developed, preparatory to residual stress determinations.

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Linear Structural Trends and Multi-Phase Intergrowths in Helvine-Group Minerals, (Zn,Fe,Mn)8[Be6Si6O24]S2

Minerals ◽

10.3390/min11030325 ◽

2021 ◽

Vol 11 (3) ◽

pp. 325

Author(s):

Sytle Antao

Keyword(s):

Cell Parameter ◽

Structural Parameters ◽

Unit Cell ◽

Fluid Composition ◽

Ternary Solid Solution ◽

X Ray Diffraction ◽

X Ray ◽

The Difference ◽

Multi Phase ◽

And Diffusion

Synchrotron high-resolution powder X-ray diffraction (HRPXRD) and Rietveld structure refinements were used to examine the crystal structure of single phases and intergrowths (either two or three phases) in 13 samples of the helvine-group minerals, (Zn,Fe,Mn)8[Be6Si6O24]S2. The helvine structure was refined in the cubic space group P4¯3n. For the intergrowths, simultaneous refinements were carried out for each phase. The structural parameters for each phase in an intergrowth are only slightly different from each other. Each phase in an intergrowth has well-defined unit-cell and structural parameters that are significantly different from the three endmembers and these do not represent exsolution or immiscibility gaps in the ternary solid-solution series. The reason for the intergrowths in the helvine-group minerals is not clear considering the similar radii, identical charge, and diffusion among the interstitial M cations (Zn2+, Fe2+, and Mn2+) that are characteristic of elongated tetrahedral coordination. The difference between the radii of Zn2+ and Mn2+ cations is 10%. Depending on the availability of the M cations, intergrowths may occur as the temperature, pressure, fugacity fS2, and fluid composition change on crystallization. The Be–Si atoms are fully ordered. The Be–O and Si–O distances are nearly constant. Several structural parameters (Be–O–Si bridging angle, M–O, M–S, average <M–O/S>[4] distances, and TO4 rotational angles) vary linearly with the a unit-cell parameter across the series because of the size of the M cation.

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Atomic structure and phason modes of the Sc–Zn icosahedral quasicrystal

IUCrJ ◽

10.1107/s2052252516007041 ◽

2016 ◽

Vol 3 (4) ◽

pp. 247-258 ◽

Cited By ~ 11

Author(s):

Tsunetomo Yamada ◽

Hiroyuki Takakura ◽

Holger Euchner ◽

Cesar Pay Gómez ◽

Alexei Bosak ◽

...

Keyword(s):

Atomic Structure ◽

Diffuse Scattering ◽

Waller Factor ◽

Close Packing ◽

Icosahedral Quasicrystal ◽

X Ray Diffraction ◽

X Ray ◽

Large Atom ◽

Debye Waller Factor ◽

The Difference

The detailed atomic structure of the binary icosahedral (i) ScZn7.33quasicrystal has been investigated by means of high-resolution synchrotron single-crystal X-ray diffraction and absolute scale measurements of diffuse scattering. The average atomic structure has been solved using the measured Bragg intensity data based on a six-dimensional model that is isostructural to the i-YbCd5.7one. The structure is described with a quasiperiodic packing of large Tsai-type rhombic triacontahedron clusters and double Friauf polyhedra (DFP), both resulting from a close-packing of a large (Sc) and a small (Zn) atom. The difference in chemical composition between i-ScZn7.33and i-YbCd5.7was found to lie in the icosahedron shell and the DFP where in i-ScZn7.33chemical disorder occurs on the large atom sites, which induces a significant distortion to the structure units. The intensity in reciprocal space displays a substantial amount of diffuse scattering with anisotropic distribution, located around the strong Bragg peaks, that can be fully interpreted as resulting from phason fluctuations, with a ratio of the phason elastic constantsK2/K1= −0.53,i.e.close to a threefold instability limit. This induces a relatively large perpendicular (or phason) Debye–Waller factor, which explains the vanishing of `high-Qperp' reflections.

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Compositional Modulation and its Optoelectric Properties of Zn(S,Se,Te) Crystals Grown by Hydrogen Radical-Enhanced CVD

MRS Proceedings ◽

10.1557/proc-417-253 ◽

1995 ◽

Vol 417 ◽

Author(s):

Hiroyuki Fujiwara ◽

Toshihiro Ii ◽

Isamu Shimizu

Keyword(s):

Deep Level ◽

Chemical Vapor ◽

X Ray Diffraction ◽

Small Shift ◽

X Ray ◽

Compositional Modulation ◽

Peak Energy ◽

Large Lattice ◽

The Difference ◽

Hydrogen Radical

AbstractHigh-quality (ZnS)n(ZnSe)12n and (ZnSe)n(ZnTe)11n (n=1∼4) crystals were grown at a low temperature of 200°C by hydrogen radical-enhanced chemical vapor deposition. From satellite peaks in x-ray diffraction spectra, these periodic structure crystals were confirmed to be grown coherently on substrates, in spite of large lattice mismatches between the grown layers and the substrates (͛=4∼7%). In photoluminescence (PL) spectra of these films, strong band-edge emissions were predominantly observed, resulting from a suppression of deep-level emissions. We found that the PL peak energy of (ZnSe)n(ZnTe)11n shifts systematically to lower energy by 200 meV with changes in the number of ZnSe layers (n), while relatively small shift of 13 meV was observed in (ZnS)n(ZnSe)12n. These discrepancy can be attributed to the difference of band-lineups or chemical natures of constituent atoms in these crystals.

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