scholarly journals Computer Programs for Standardless Quantitative Analysis of Minerals Using the Full Powder Diffraction Profile

1991 ◽  
Vol 6 (1) ◽  
pp. 2-9 ◽  
Author(s):  
J. C. Taylor
Keyword(s):  
Crystal Structure ◽  
Quantitative Analysis ◽  
Least Squares ◽  
Powder Diffraction ◽  
Profile Analysis ◽  
Unit Cell ◽  
Diffraction Profile ◽  
Pattern Processing ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractA Fortran 77 computer program has been developed for the quantitative analysis of minerals by multiphase profile analysis of the complete powder diffraction pattern. Featured are full-matrix least-squares refinement of 14 Rietveld “instrumental parameters” (phase scales, asymmetry, preferred orientations (March model), linewidths, instrument zero, lineshapes and unit cell dimensions), Brindley particle absorption contrast factors and amorphicity corrections. The program uses a crystal structure Databank, which contains information on absorption coefficients, unit cell data and crystal structures for some 90 common minerals. New minerals can be easily added. Structure parameters are also refinable by a profile decomposition method using a program called STRUCT. The sum of the calculated patterns, derived from the crystal structure data, is fitted to the observed pattern by a program called TRACSCAL which runs in singlepass multiphase mode and, after the above corrections have been applied, the weight percentages of the component phases are calculated from the Rietveld scaling factors.The program runs on an IBM-compatible AT computer with 640K of RAM, on an extended memory AT, or a mainframe system. Examples of its use are given with standard mixtures and naturally occurring specimens. On an AT computer with 20MHz clock speed a scaling run, including data input, reading of the pattern, processing of (hkl) files, calculation of the profile and one cycle of least squares fitting takes about 30 seconds for binary standard mixtures and about 2.5 minutes for a 7-phase natural bauxite pattern containing 320 independent (hkl) reflections.

Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

Refinement of the Crystal Structure of Synthetic Chervetite, Pb2V2O7

1973 ◽  
Vol 51 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Robert D. Shannon ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Unit Cell ◽  
Type Structure ◽  
Covalent Bonds ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The structure of synthetic chervetite has been refined by full matrix least-squares to a ωR = 0.029 using 1105 reflections. Unit cell dimensions are a = 13.3689(7), b = 7.1607(4), c = 7.1027(4) Å, β = 105935(5)°, and the space group is P21/a. The structure, originally solved by Kawahara, is a dichromate-type structure with a V2O74− group eclipsed to within 11 ± 5°. The Pb2+ ions are irregularly coordinated to 8 or 9 oxygens with distances from 2.40 to 3.20 Å. The distortion of the Pb–O distances is considerably greater than the corresponding distortions of the Sr–O distances in the similar β-Sr2V2O7 structure and is related to the tendency of Pb2+ to form directional covalent bonds. The V–O distances range from 1,665 to 1.720 Å for terminal oxygens and are 1.812 and 1.821 Å for the bridging oxygens. The V–O distances are consistent with the strengths of the Pb—O bonds.

The crystal structure of benzenediazonium tetrafluoroborate, C6H5N2+•BF4−1

1982 ◽  
Vol 60 (22) ◽  
pp. 2852-2855 ◽  
Author(s):  
Miroslaw Cygler ◽  
Maria Przybylska ◽  
Richard MacLeod Elofson
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Benzene Ring ◽  
Positive Charge ◽  
Unit Cell ◽  
Full Matrix ◽  
Bond Lengths ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Close Contacts

Benzenediazonium tetrafluoroborate, C6H5N2+•BF4−, crystallizes in space group P21/a with unit cell dimensions a = 17.347(2), b = 8.396(1), c = 5.685(1) Å, β = 92.14(1)°, Z = 4. The structure was solved by direct phasing methods using the program SHELX 76. The parameters were refined by full-matrix least-squares to a final R = 0.063 for 1346 observed reflections. The bond lengths and angles agree very well with those of Rømming for benzenediazonium chloride. The C—N and N≡N bond lengths are 1.415(3) and 1.083(3) Å, respectively, and the bonds of the benzene ring do not show any significant differences as they vary from 1.371(5) to 1.383(4) Å. There are three [Formula: see text] close contacts of ≤ 2.84 Å and the positive charge appears to be shared between the nitrogen atoms.

scholarly journals Molekül- und Kristallstruktur von C7H7Mo(CO)2-SnCl3 / The Crystal Structure of C7H7Mo(CO)2-SnCl3

1975 ◽  
Vol 30 (1-2) ◽  
pp. 22-25 ◽  
Author(s):  
M. L. Ziegler ◽  
H.-E. Sasse ◽  
B. Nuber
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Title Compound ◽  
Three Dimensional ◽  
Unit Cell ◽  
Fourier Methods ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Group D

The structure of the title compound has been determined from three dimensional X-ray data by Patterson and Fourier methods. The crystals are orthorombic, with unit cell dimensions a = 1181,50 pm, b = 943,68 pm, c = 1181,50 pm, space group D2h16 and Z = 4. Least squares refinement, by use of 1540 independent reflections measured on a diffractometer has reached R = 5,9%.There are discrete C7H7Mo(CO)2 SnCl3 molecules, the molybdenum-tin bond has been dicussed together with the corresponding bonds in other C7H7Mo(CO)2 SnR3 compounds.

Unit-Cell Dimensions of Two-Dimensionai Clay Minerals

1989 ◽  
Vol 4 (1) ◽  
pp. 19-20 ◽  
Author(s):  
Peter Bayliss
Keyword(s):  
Least Squares ◽  
Clay Minerals ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Powder Diffraction File ◽  
Hexagonal System ◽  
Cell Dimensions ◽  
Mineral Powder ◽  
Unit Cell Dimensions ◽  
Layer Groups

AbstractThe unit cell dimensions of minerals in the smectite group, regular and random mixed-layer groups, and halloysite shown in the Mineral Powder Diffraction File (1986) have been refined by least-squares analysis in the hexagonal system with a primitive lattice with indices restricted to hk or 00l reflections. Trioctahedral minerals have larger a unit-cell dimensions than dioctahedral minerals.

The Crystal Structure of a Thiathiophthen Nitrogen Isostere, 3,5-Epidithio-2,5-diphenyl-2,4-pentadienylidene-3-aminoquinoline

1971 ◽  
Vol 49 (2) ◽  
pp. 167-172 ◽  
Author(s):  
F. Leung ◽  
S. C. Nyburg
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
X Ray ◽  
Bond Lengths ◽  
Triclinic System ◽  
R Factor ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

The crystal structure of a thiathiophthen nitrogen isostere (7) has been solved by X-ray analysis. The crystal belongs to the triclinic system with unit cell dimensions: a = 11.275(11), b = 9.558(10), c = 10.797(10) Å, α = 92.50(10), β = 116.98(10), γ = 92.61(10)°. There are two molecules per unit cell, space group [Formula: see text]. The data were collected by diffractometer with CuKα radiation. The structure was solved by symbolic addition procedures, and fully refined anisotropically using full-matrix least squares to an R factor of 6.3%.The S—S and S—N bond lengths were found to be 2.364 and 1.887 Å, respectively. This reveals the partial bonding character between S … S … N atoms.

Improved Crystallographic Data for AlNbO4

1991 ◽  
Vol 6 (1) ◽  
pp. 48-49 ◽  
Author(s):  
C. J. Rawn ◽  
R. S. Roth ◽  
H. F. McMurdie
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Crystallographic Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Monoclinic Cell

AbstractThe compound AlNbO4 has been studied by single crystal X-ray precession photographs and X-ray powder diffraction. Unit cell dimensions were calculated using a least squares analysis that refined to a Δ2θ° of no more than 0.03°. A monoclinic cell was found with space group C2/m, a = 12.1558(5)Å, b = 3.7345(2)Å, c = 6.4886(3)Å, and β = 107.613(4)°.

Kristallstruktur von Bis(N.N′-bis(8-chinoyl)äthylendiaminato)nickel(II) / Crystal Structure of Bis(N,N′-bis(8-chinoyl)ethylenediaminato)nickel(II)

1977 ◽  
Vol 32 (2) ◽  
pp. 131-133 ◽  
Author(s):  
H. Endres ◽  
H. J. Keller ◽  
A. Poveda
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Least Squares ◽  
Title Compound ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Cell Dimensions ◽  
Planar Molecules ◽  
Unit Cell Dimensions

The title compound NiC20H16N4 crystallizes in the monoclinic space group Ρ21/a with unit cell dimensions a = 12.07(2) Å, b= 10.712(4) Å, c = 13.50(3) Å, β= 113.1(1)°. The structure was refined by a blockmatrix least squares procedure to R = 0.126, based on 1258 observed intensities. The planar molecules form centro-symmetric dimers in the solid state with interplane distances of 3.3 A.

Cyclopentadienyl-Ruthenium and -Osmium Chemistry. XXX. Synthesis and X-Ray Structure of [Ru(dppm-P)(dppm-P,P')(η-C5H5)][PF6]0.5[PO2F2]0.5

1988 ◽  
Vol 41 (4) ◽  
pp. 597 ◽  
Author(s):  
MI Bruce ◽  
MP Cifuentes ◽  
KR Grundy ◽  
MJ Liddell ◽  
MR Snow ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Phenyl Group ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
One Pot ◽  
Full Matrix ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

An improved, one-pot synthesis is reported for the [Ru (dppm -P)(dppm -P, P′)(η-C5H5)]+ cation as its BF4- salt. The crystal structure of [Ru ( dppm - P)( dppm -P,P′)(η-C5H5)]+, obtained as the mixed PF6-/PO2F2- salt, has also been determined. There are few differences in dimensions between the mono- and bi-dentate dppm ligands; chelation sharply reduces the P-CH2-P angle, and one phenyl group on each phosphorus is bent away from the metal. Crystals are monoclinic, space group C2/c with unit cell dimensions a 21.743(3), b 23.594(3), c 21.352(3)Ǻ, β 110.17(1) and Z 8. The structure was refined by a full-matrix least-squares procedure to final R 0.078 and Rw 0.087 for 4490 reflections with I > 2.5σ(I).

Crystal data and X-ray powder diffraction data of 2,4-diiodo-4-nitrophenol (disophenol), C6H3I2NO3. More precise X-ray powder diffraction data of p-nitrophenol, C6H5NO3

1996 ◽  
Vol 11 (4) ◽  
pp. 301-304
Author(s):  
Héctor Novoa de Armas ◽  
Rolando González Hernández ◽  
José Antonio Henao Martínez ◽  
Ramón Poméz Hernández
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Monoclinic Cell

p-nitrophenol, C6H5NO3, and disophenol, C6H3I2NO3, have been investigated by means of X-ray powder diffraction. The unit cell dimensions were determined from diffractometer methods, using monochromatic CuKα1 radiation, and evaluated by indexing programs. The monoclinic cell found for p-nitrophenol was a=6.159(2) Å, b=8.890(2) Å, c=11.770(2) Å, β=103.04(2)°, Z=4, space group P21 or P2l/m, Dx=1.469 Mg/m3. The monoclinic cell found for disophenol has the dimensions a=8.886(1) Å, b=14.088(2) Å, c=8.521(1) Å, β=91.11(1)°, Z=4, space group P2, P2, Pm or P2/m, Dx=2.438 Mg/m3.

Sign in / Sign up

Export Citation Format

Share Document