Site-occupancy scheme in disordered Ca3RE2(BO3)4: a dependence on rare-earth (RE) ionic radius

2021 ◽  
Vol 77 (3) ◽  
Author(s):  
Katarzyna M. Kosyl ◽  
Wojciech Paszkowicz ◽  
Roman Minikayev ◽  
Alexey N. Shekhovtsov ◽  
Miron B. Kosmyna ◽  
...  
Keyword(s):  
Rare Earth ◽  
Ionic Radius ◽  
Site Occupancy ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
X Ray ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The structures of polycrystalline Ca3RE2(BO3)4 (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y; space group Pnma) orthoborates were determined using powder X-ray diffraction. Trends in the unit-cell dimensions and yet unreported trends in other structural properties (interatomic distances and the fractional occupation of three Ca/RE sites) for these compounds are demonstrated as a function of RE ionic radius. The unit-cell volume and a unit-cell parameter present a linear dependence, while the b and c unit-cell parameters change in a nonlinear manner. For the whole series, the RE atoms are present at all three cationic sites (labelled as M1, M2 and M3), but the fractional occupancies depend on the RE ionic radius. The small rare-earth atoms tend to enter mainly the M3 site; for the larger rare earths, the occupancy of this site decreases sharply. The occupancy of the M1 site by RE atoms is around 0.5 and tends to increase with increasing RE ionic radius. The M2 site is the least preferentially occupied by RE ions, but the occupancy discernibly increases with rising radius as well. These findings are assembled with properties of isostructural strontium and barium borates, allowing prediction of occupancy schemes for not yet investigated compounds from the A 3RE2(BO3)4 (A = Ca, Ba, Sr).

scholarly journals The crystal structures of two polyamides (‘nylons’)

1947 ◽  
Vol 189 (1016) ◽  
pp. 39-68 ◽  
Keyword(s):  
Crystal Structures ◽  
Unit Cell ◽  
Chain Molecule ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Dimensions ◽  
C Fibre ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Crystalline Forms

Detailed interpretations of the X -ray diffraction patterns of fibres and sheets of 66 and 6.10 polyamides (polyhexam ethylene adipamide and sebacamide respectively) are proposed. The crystal structures of the two substances are completely analogous. Fibres of these two polyam ides usually contain two different crystalline forms, α and β, which are different packings of geometrically similar molecules; most fibres consist chiefly of the α form. In the case of the 66 polymer, fibres have been obtained in which there is no detectable proportion of the β form. Unit cell dimensions and the indices of reflexions for the α form were determined by trial, using normal fibre photographs, and were checked by using doubly oriented sheets set at different angles to the X -ray beam. The unit cell of the a form is triclinic, with a — 4·9 A, b = 5·4 A, c (fibre axis) = 17·2A, α = 48 1/2º, β = 77º, γ = 63 1/2º for the 66 polymer; a = 4·95A, b = 5·4A, c (fibre axes) = 22·4A, α = 49º, β = 76 1/2º, γ = 63 1/2º for the 6.10 polymer. One chain molecule passes through the cell in both cases. Atomic coordinates in occrystals were determined by interpretation of the relative intensities of the reflexions. The chains are planar or very nearly so; the oxygen atoms appear to lie a little off the plane of the chain. The molecules are linked by hydrogen bonds between C = 0 and NH groups, to form sheets. A simple packing of these sheets of molecules gives the α arrangement.

Crystal Data for Complexes of Co(II) and Ni(II) Perchlorates with Mepirizole

1992 ◽  
Vol 7 (3) ◽  
pp. 166-168
Author(s):  
J.M. Amigó ◽  
L.E. Ochando ◽  
M.M. Reventós ◽  
J. García-Lozano ◽  
L. Soto-Tuero
Keyword(s):  
Powder Diffraction ◽  
Unit Cell ◽  
Crystal Data ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractMetal mepirizole perchlorates, M(C11H14N4O2)3 (C104)2 where M = Co(II) and Ni(II) have been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined by indexing programs from diffractometer data. Refined cell parameters (monoclinic with a C-centered cell), calculated density and Z values are presented.

Unit cell dimensions of the hydrated aluminium phosphate–sulphate minerals sanjuanite, kribergite, and hotsonite

1989 ◽  
Vol 53 (371) ◽  
pp. 385-386 ◽  
Author(s):  
H. De Bruiyn ◽  
G. J. Beukes ◽  
W. A. Van Der Westhuizen ◽  
E. A. W. Tordiffe
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Aluminium Phosphate ◽  
Powder Diffraction File ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Unit Cells ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Hydrated Aluminium

AT the time when the hydrated aluminium phosphate-sulphate hotsonite (Beukes et al., 1984a) and its equally rare relative zaherite (Beukes et al., 1984b; De Bruiyn et al., 1985) were discovered near Pofadder, South Africa, very little was known about the unit cells of the other two hydrated aluminium phosphate-sulphate minerals sanjuanite and kribergite, originally described by De Abeledo et al. (1968) from Argentina and Sweden, respectively. Although the Powder Diffraction file (PDF) contains the X-ray diffraction patterns for sanjuanite and kribergite (PDF 20-47 and 20-48 respectively), they had not been indexed nor have their unit cell parameters been calculated thus far.

Synthesis and crystal structure of Na3.5Cr1.5Co0.5(PO4)3 phosphate

2006 ◽  
Vol 21 (3) ◽  
pp. 210-213 ◽  
Author(s):  
Mohamed Chakir ◽  
Abdelaziz El Jazouli ◽  
Jean-Pierre Chaminade
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
X Ray ◽  
Hexagonal Unit Cell ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

A new Nasicon phosphates series [Na3+xCr2−xCox(PO4)3(0⩽x⩽1)] was synthesized by a coprecipitation method and structurally characterized by powder X-ray diffraction. The selected compound Na3.5Cr1.5Co0.5(PO4)3 (x=0.5) crystallizes in the R3c space group with the following hexagonal unit-cell dimensions: ah=8.7285(3) Å, ch=21.580(2) Å, V=1423.8(1) Å3, and Z=6. This three-dimensional framework is built of PO4 tetrahedra and Cr∕CoO6 octahedra sharing corners. Na atoms occupy totally M(1) sites and partially M(2) sites.

The CdO–CdCl2 reaction studied by thermal analysis and X-ray diffraction: X-ray diffractogram and infrared spectrum of CdCl2•2CdO

1969 ◽  
Vol 47 (6) ◽  
pp. 1045-1050 ◽  
Author(s):  
P. Ramamurthy ◽  
E. A. Secco
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Infrared Spectrum ◽  
Band Structure ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Orthorhombic System ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

CdO and molten CdCl2 react to form CdCl2•2CdO according to the equation:[Formula: see text]The compound CdCl2•2CdO dissociates to the oxide and chloride at 680 °C. CdO and CdCl2 form a solid solution of partial miscibility of 15% by weight of CdO.The X-ray diffractogram of CdCl2•2CdO was indexed to the orthorhombic system. The unit cell dimensions are calculated to be a = 4.38 Å, b = 11.47 Å, c = 9.93 Å with 4 molecules in the unit cell. The infrared spectrum shows a band structure of two doublets and a well-defined band in the region 370–550 cm−1.

Infrared and Raman spectra and X-ray diffraction studies of solid lead(II) carbonates

1983 ◽  
Vol 61 (3) ◽  
pp. 494-502 ◽  
Author(s):  
Murray H. Brooker ◽  
S. Sunder ◽  
Peter Taylor ◽  
Vincent J. Lopata
Keyword(s):  
Unit Cell ◽  
Spectral Features ◽  
Infrared And Raman Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Carbonate Ions ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Sodium And Potassium

Four basic lead carbonates were prepared and identified by X-ray powder diffractometry. These were hydrocerussite (Pb3(OH)2(CO3)2), plumbonacrite (Pb10O(OH)6(CO3)6), and the two adducts MOH•2PbCO3 (M = Na, K). New diffraction data are presented for the latter two compounds; they both have primitive hexagonal lattices with two formula units per unit cell. The unit cell dimensions of the sodium and potassium compounds are a = 5.273 ± 0.002 Å, c = 13.448 ± 0.005 Å and a = 5.348 ± 0.002 Å, c = 13.990 ± 0.005 Å, respectively. Six possible space groups are discussed.Raman and infrared spectra are reported for all four compounds, and compared with those of cerussite (PbCO3); assignment of the spectral features is discussed. Vibrational spectra of the two MOH adducts indicate that they are isostructural, and that the structure contains a well-defined lead sub-lattice, consistent with the X-ray data. The spectra of hydrocerussite and plumbonacrite indicate that lead is present as oxygen-bridged polymeric moieties in these solids. The carbonate ions occupy two and three independent sites in hydrocerussite and plumbonacrite, respectively.

X-ray powder diffraction pattern for lactitol and lactitol monohydrate

1994 ◽  
Vol 9 (3) ◽  
pp. 213-216 ◽  
Author(s):  
J. Valkonen ◽  
P. Perkkalainen ◽  
I. Pitkänen ◽  
H. Rautiainen
Keyword(s):  
Powder Diffraction ◽  
Least Squares Method ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions

Diffraction patterns were recorded, and unit cell dimensions refined by the least-squares method, for lactitol and lactitol monohydrate. Refined unit cell parameters for lactitol are: a =7.622(1) Å, b = 10.764(2) Å, c = 9.375(1) Å, β= 108.25(1)° in space group P21, and those for lactitol monohydrate a =7.844(1) Å, b = 12.673(2) Å, c = 15.942(2) Å in space group P212121.

scholarly journals Chemical Preparation, Thermal Behavior and IR Studies of the New Chromium Diphosphate Hydrate and Crystal Structure of its Corresponding Anhydrous

2021 ◽  
Vol 11 (5) ◽  
pp. 13412-13420
Keyword(s):  
Thermal Behavior ◽  
Absorption Spectrometry ◽  
Unit Cell ◽  
Ir Absorption ◽  
X Ray Diffraction ◽  
Chemical Preparation ◽  
X Ray ◽  
Ir Studies ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Chemical preparation, thermal behavior, and IR studies are given for the diphosphate Cr4(P2O7)3.28H2O and its anhydrous form Cr4(P2O7)3. Cr4(P2O7)3.28H2O, is monoclinic P2/m with the following unit-cell dimensions : a = 16.169(1)Å, b = 9.336(5)Å, c = 9.446(4)Å, β = 124.796(5)°, and Z = 4. The total dehydration of Cr4(P2O7)3.28H2O, between 90°C and 450°C, leads to its anhydrous form, Cr4(P2O7)3. Cr4(P2O7)3 is isotopic to V4(P2O7)3, crystallizing in the orthorhombic system, space group Pmcn, Z = 4 with the following unit-cell dimensions: a = 7.25(2), b = 9.38(1)Å and c = 21.00(4)Å. Cr4(P2O7)3 is stable until its melting point at 1050°C. The thermal behavior of Cr4(P2O7)3.28H2O has been investigated and interpreted by comparison with IR absorption spectrometry and X-ray diffraction experiments.

Basic halides and related species of molybdenum(III). I. The empirical formulae and unit cell dimensions of the basic halides

1976 ◽  
Vol 29 (4) ◽  
pp. 711 ◽  
Author(s):  
DJ Stabb
Keyword(s):  
Evolved Gas Analysis ◽  
Gas Analysis ◽  
Unit Cell ◽  
Water Molecules ◽  
Orthorhombic Unit Cell ◽  
Evolved Gas ◽  
X Ray ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The basic halides MoOX(H2O), (X = F, Cl) were examined by vacuogravimetric and evolved gas analysis and by X-ray and electron diffraction techniques. The basic chloride prepared by slow crystallization had y = 3.08, with an orthorhombic unit cell 0.723 by 0.820 by 1.805 nm. Basic chlorides produced by rapid precipitation were less crystalline, of slightly larger unit cell dimensions and had 3.0 < y < 4.3. The water in excess of y = 3 was loosely held, while three water molecules per molybdenum were more strongly held. The fluoride, which could not be obtained with the perfect MoOF(H2O)3 stoichiometry, was isomorphous (cell parameters 0.710 by 0.823 by 1.824 nm for [MoOF0.96(OH)0.04(H2O)3] (H2O)0.28). It is concluded that the only hydrate of MoOX existing under normal conditions is MoOX(H2O)3, not the previously reported tetrahydrate.

X-RAY DIFFRACTION DATA FOR ALKALI DITHIONATES

1963 ◽  
Vol 41 (2) ◽  
pp. 219-223 ◽  
Author(s):  
D. W. Larson ◽  
A. B. VanCleave
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Dimensions ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions

X-Ray powder diffraction patterns have been recorded for the alkali dithionates and for barium and ammonium dithionate. The patterns have been indexed and unit cell dimensions determined for lithium dithionate dihydrate, sodium dithionate (anhydrous), and rubidium dithionate. Previously determined cell dimensions have been confirmed in other cases.

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