Determination of nanoparticle structure type, size and strain distribution from X-ray data for monatomic f.c.c.-derived non-crystallographic nanoclusters

2003 ◽  
Vol 36 (5) ◽  
pp. 1148-1158 ◽  
Author(s):  
Antonio Cervellino ◽  
Cinzia Giannini ◽  
Antonietta Guagliardi
Keyword(s):  
Structure Type ◽  
X Ray Diffraction ◽  
Debye Function ◽  
X Ray ◽  
Profile Fitting ◽  
Type Size ◽  
Nanoparticle Structure ◽  
Diffraction Patterns ◽  
Specific Material ◽  
Log Normal

Whole-profile-fitting least-squares techniques are applied to simulated and experimental X-ray diffraction patterns of monatomic face-centred cubic (f.c.c.)-derived non-crystallographic nanoclusters to extract structure and size information. Three main structure types have been considered (cuboctahedral, icosahedral and decahedral). Nanocluster structure models have been generated within an original mathematical approach so as to be independent of a specific material. For each structure type, a log-normal size distribution is assumed and a phenomenological function is introduced to model possible additional size-related strain effects. The Debye function method (modified to increase computational efficiency) has been used to obtain the diffracted intensities of the nanocluster. Tests revealed the effectiveness of the method to recognize the structure types correctly and to estimate with good accuracy structure concentrations and size distributions. Application to a thiol-passivated gold nanoparticle sample is presented.

Comments on determining X-ray diffraction-based volume fractions of retained austenite in steels

2001 ◽  
Vol 16 (4) ◽  
pp. 198-204 ◽  
Author(s):  
C. K. Lowe-Ma ◽  
W. T. Donlon ◽  
W. E. Dowling
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Profile Fitting ◽  
Diffraction Peaks ◽  
Diffraction Patterns ◽  
Heat Treatment Regimes ◽  
Integrated Intensities

Retained austenite is an important characteristic of properly heat-treated steel components, particularly gears and shafts, that will be subjected to long-term use and wear. Normally, either X-ray diffraction or optical microscopy techniques are used to determine the volume percent of retained austenite present in steel components subjected to specific heat-treatment regimes. As described in the literature, a number of phenomenological, experimental, and calculation factors can influence the volume fraction of retained austenite determined from X-ray diffraction measurements. However, recent disagreement between metallurgical properties, microscopy, and service laboratory values for retained austenite led to a re-evaluation of possible reasons for the apparent discrepancies. Broad, distorted X-ray peaks from un-tempered martensite were found to yield unreliable integrated intensities whereas diffraction peaks from tempered samples were more amenable to profile fitting with standard shape functions, yielding reliable integrated intensities. Retained austenite values calculated from reliable integrated intensities were found to be consistent with values obtained by Rietveld refinement of the diffraction patterns. The experimental conditions used by service laboratories combined with a poor choice of diffraction peaks were found to be sources of retained austenite values containing significant bias.

Structure, Diffraction and Energetic Stability of the Spinel form of LiCoO2

1992 ◽  
Vol 293 ◽  
Author(s):  
J. N. Reimers ◽  
W. Li ◽  
E. Rossen ◽  
J. R. Dahn
Keyword(s):  
Lattice Gas ◽  
Structure Type ◽  
Convincing Evidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Diffraction Patterns ◽  
Spinel Structures ◽  
Formation Energies ◽  
New Phase

AbstractA recently reported new phase of LiCoO2, called LT-LiCoO2 (LT stands for Low Temperature) by the discoverers, was synthesized at 400°C and studied using X-ray diffraction and electrochemical de-intercalation of lithium. The first reports of LT-LiCoO2 give convincing evidence that the compound is layered with the same structure type as LiCoO2 prepared at 850°C (HT-LiCoO2). However, the electrochemical properties of LT and HT LiCoO2 are markedly different, which is hard to understand if the crystal structures are almost the same. A better understanding of the diffraction and electrochemical data is attained if the LT structure is assumed to be spinel related analogous to Li2Ti2O4. We show that the layered structure (with suitable lattice constants and layer spacings) and spinel structure give identical powder diffraction patterns. We also show that the formation energies of the layered and spinel structures are also identical using a lattice gas model with pair-wise atom-atom interactions.

Kyzylkumite, Ti2V3+O5(OH): new structure type, modularity and revised formula

2013 ◽  
Vol 77 (1) ◽  
pp. 33-44 ◽  
Author(s):  
T. Armbruster ◽  
B. Lazic ◽  
L. Z. Reznitsky ◽  
E. V. Sklyarov
Keyword(s):  
Structure Type ◽  
Close Packing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrogen Atom Position ◽  
Diffraction Patterns ◽  
Modular Structures ◽  
The Relationship ◽  
Atom Position ◽  
South Baikal

AbstractThe crystal structure of kyzylkumite, ideally Ti2V3+O5 (OH), from the Sludyanka complex in South Baikal, Russia was solved and refined (including the hydrogen atom position) to an agreement index, R1, of 2.34% using X-ray diffraction data collected on a twinned crystal. Kyzylkumite crystallizes in space group P21/c, with a = 8.4787(1), b = 4.5624(1), c = 10.0330(1) Å , β = 93.174(1)º, V = 387.51(1) Å3 and Z = 4. Tivanite, TiV3+O3OH, and kyzylkumite have modular structures based on hexagonal close packing of oxygen, which are made up of rutile [TiO2] and montroseite [V3+O(OH)] slices. In tivanite the rutile:montroseite ratio is 1:1, in kyzylkumite the ratio is 2:1. The montroseite module may be replaced by the isotypic paramontroseite V4+O2 module, which produces a phase with the formula Ti2V4+O6. In the metamorphic rocks of the Sludyanka complex, vanadium can be present as V4+ and V3+ within the same mineral (e.g.in batisivite, schreyerite and berdesinskiite). Kyzylkumite has a flexible composition with respect to the M4+/M3+ ratio. The relationship between kyzylkumite and a closely related Be-bearing kyzylkumite-like mineral with an orthorhombic norbergite-type structure from Byrud mine, Norway is discussed. Both minerals have similar X-ray powder diffraction patterns.

scholarly journals Silicon in Fe-Si Alloys: Correction of X-Ray Intensities for Preferred Orientation

1997 ◽  
Vol 29 (1-2) ◽  
pp. 77-87
Author(s):  
M. O. Figueiredo ◽  
F. Margarido
Keyword(s):  
Preferred Orientation ◽  
Correction Procedure ◽  
X Ray Diffraction ◽  
Silicon Phase ◽  
X Ray ◽  
Orientation Effects ◽  
Profile Fitting ◽  
Previous Algorithm ◽  
Texture Effect ◽  
Diffraction Patterns

A texture effect in the silicon phase of industrial Fe-Si alloys was noticed in the X-ray diffraction patterns through the reinforcement of the 111 reflection. A similar effect was also apparent in a commercial silicon standard pellet used as reference material and supposed to be texture-free.A quick correction procedure to account for preferred orientation effects was developed, based on a previous algorithm currently applied for the automatic profile fitting of powder diffractometer data. “Modified Wilson plots” are established for visualizing the efficiency of texture correction according to the proposed method.

Cu3Sn – understanding the systematic absences

2014 ◽  
Vol 70 (5) ◽  
pp. 879-887 ◽  
Author(s):  
Carola J. Müller ◽  
Sven Lidin
Keyword(s):  
Intermetallic Compound ◽  
Antiphase Boundary ◽  
Structure Type ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Long Period ◽  
Diffraction Patterns

The intermetallic compound Cu3Sn has previously been described as a long-period antiphase boundary superstructure of the Cu3Ti structure type. While the compound itself has been reported as a tenfold and an eightfold superstructure, ternary doped alloys show shorter repetitions. Interestingly, the diffraction patterns of these compounds show non-crystallographic absences that cannot be explained using the superstructure models. Since the compound exhibits phase broadening, these models are not satisfactory because the paucity of observed data does not allow for a refinement of the composition. Here, an alternative, superspace model in the orthorhombic space groupXmcm(0β0)000 is proposed, with the centering vectors (0,0,0,0) and (½,0,0,½). The presence of the non-crystallographic absences is explained as a result of a dominating occupational modulation that is accompanied by a weaker displacive modulation. In consistency with the EDXS results, the composition has been refined to Cu3 + xSn from single-crystal X-ray diffraction data. It is further demonstrated that by varying the length and the direction of the modulation wavevector in the superspace model, the ternary Cu3Sn compounds and other colored hexagonal close packing (h.c.p.) structures can be produced.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Examination of Rabbit Fc Crystals

1968 ◽  
Vol 26 ◽  
pp. 140-141
Author(s):  
J. P. Robinson ◽  
P. G. Lenhert
Keyword(s):  
Molecular Weight ◽  
Flat Plate ◽  
Phosphate Buffer ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutral Ph ◽  
Small Crystals ◽  
Carbon Coated ◽  
Diffraction Patterns

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Infrared spectroscopic study of the YPO4-YCrO4 system

1985 ◽  
Vol 50 (10) ◽  
pp. 2139-2145
Author(s):  
Alexander Muck ◽  
Eva Šantavá ◽  
Bohumil Hájek
Keyword(s):  
Spectroscopic Study ◽  
Infrared Spectra ◽  
Point Of View ◽  
Mixed Crystals ◽  
Crystal Symmetry ◽  
Infrared Spectroscopic Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infrared Spectroscopic ◽  
Diffraction Patterns

The infrared spectra and powder X-ray diffraction patterns of polycrystalline YPO4-YCrO4 samples are studied from the point of view of their crystal symmetry. Mixed crystals of the D4h19 symmetry are formed over the region of 0-30 mol.% YPO4 in YCrO4. The Td → D2d → D2 or C2v(GS eff) correlation is appropriate for both PO43- and CrO43- anions.

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