LCBASE: Program and database for phase identification

1994 ◽  
Vol 9 (2) ◽  
pp. 136-142
Author(s):  
W. Paszkowicz ◽  
A. Makosa
Keyword(s):  
Diffraction Data ◽  
Single Phase ◽  
Unit Cell ◽  
Electron Diffraction Data ◽  
Bravais Lattice ◽  
Phase Identification ◽  
Solubility Range ◽  
Inorganic Substances ◽  
Cell Dimensions ◽  
The Difference

A computer program for phase identification using powder diffraction data is presented. It works with a small database containing the unit-cell dimensions and Bravais lattice for chosen classes of inorganic substances. The algorithm works for single phase samples and such samples in which a single phase dominates. During the search, the peak positions generated using the reference unit cells are compared with the experimental ones. Unit-cell constants of all obtained solutions are (optionally) immediately refined. Application examples show that the method gives as possible solutions those database entries for which the cell dimensions differ from the investigated sample by not more than about 0.05 Å. These entries may include the true phase or isotypical phases unless the imposed chemical constraint does not exclude them. If the sample is a solid solution, then the algorithm is able to find phases of differing chemical composition belonging to the same solubility range (provided that the difference in lattice constants is not too large). One of the examples illustrates the possibility of application for electron-diffraction data.

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.

ZrSiO4 mit monokliner Baddeleyitstruktur?.

1976 ◽  
Vol 31 (9) ◽  
pp. 1175-1178 ◽  
Author(s):  
Kurt Walenta
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Limits Of Error ◽  
Zircon Particles

A new compound having the same composition as zircon, ZrSiO4, but differing from it in its structure has been obtained by heating zircon particles to a temperature of 5000 to 10000°K. According to X-ray powder diffraction data the structure and within limits of error also the unit-cell dimensions are identical with that of monoclinic baddeleyite, ZrO2. This suggests that the baddeleyite lattice can not only accommodate 10 molecular % SiO2 as is already known for some time, but substantially more, unless it is assumed that some kind of submicroscopic exsolution of amorphous SiO2 has taken place.

Die Kristallstruktur von Methyltriphenylphosphoniumhexachlorotitanat [MePh3P]2TiCl6 / The Crystal Structure of Methyltriphenylphosphonium Hexachlorotitanate

1981 ◽  
Vol 36 (2) ◽  
pp. 135-137 ◽  
Author(s):  
Evamarie Hey ◽  
Ulrich Müller
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Unit Cell ◽  
Distorted Octahedron ◽  
Inversion Center ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions

The crystal structure of [MePh3P]2TiCl6 was determined from X-ray diffraction data and refined to a residual index of R = 0.065. It crystallizes in the space group P2i/n with two formula units per unit cell; the cell dimensions are a - 921, b = 1314, c = 1648 pm and y - 100.87°. The TiCl62- ion occupies an inversion center and has the shape of a slightly distorted octahedron with Ti-Cl distances between 233 and 235 pm.

(Ph4P)2 Mn2Br6 und (Ph3PCH2Ph)2Mn2I6 (Ph = C6H5) / (Ph4P)2Mn2Br6 and (Ph 3PCH2Ph)2Mn2I6 (Ph = C6H5

1988 ◽  
Vol 43 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Siegfried Pohl ◽  
Wolfgang Saak ◽  
Peter Stolz
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Unit Cell ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
The Mean ◽  
The Difference

(Ph4P)2Mn2Br6 (1) and (Ph3PCH2Ph)2Mn2I6 (2) were prepared from the reaction of manganese dihalide with the corresponding phosphonium halide in CH2Cl2.The structures of 1 and 2 were determined from single crystal X-ray diffraction data.Both compounds crystallize in the triclinic space group P 1 with one formula unit per unit cell.1:a = 998.1(1), b = 1005.7(1), c = 1313.3(2) pm, α = 108.51(1), β = 94.25(1), γ = 100.36(1)°.2: a = 1058.6(2), b = 1236.3(2), c = 1248.4(3) pm, α = 63.53(1), β = 74.15(1), γ = 74.65(1)°.The structures of 1 and 2 exhibit discrete, dimeric anions formed by the fusion of two identical tetrahedral-like units with a common halogen-halogen edge. The mean Mn-Hal bond lengths were found to be 251.8 pm (Mn-Br) and 272.2 pm (Mn-I). The difference between the bridging and terminal Mn-Hal bond lengths is about 12-13 pm in both compounds

Voltage dependence of the electron diffraction amplitudes in the ab initio analysis of copper perchlorophthalocyanine

1992 ◽  
Vol 50 (2) ◽  
pp. 1168-1169
Author(s):  
W.F. Tivol ◽  
J.N. Turner ◽  
D.L. Dorset
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Electron Diffraction Data ◽  
Electron Microscopic ◽  
Heavy Atoms ◽  
C And N ◽  
Diffraction Patterns ◽  
Structure Research

Copper perchlorophthalocyanine has become a model compound for exploring the application of electron microscopic and diffraction methods in high resolution molecular structure research. Because of the scattering contrast between the Cu and Cl heavy atoms and the lighter C and N atoms, it was not possible to determine the structure with electron diffraction data obtained at 100 kV a number of years ago. Dynamical scattering all but obscures the detail in the diffraction data due to the unit cell Fourier transform. Studies at 500 kV had also determined that the electron microscopic images were influenced by dynamic scattering. Since our HVEM can be operated from 100 kV to 1.2 MV in 100 kV steps, we are studying the influence of accelerating voltage on our ability to determine atomic-level molecular structure.We recorded electron diffraction patterns from crystals epitaxially oriented on KCl and tilted 26.5° relative to the beam in order to align the c-axis of the unit cell along the beam direction.

Powder diffraction data and Rietveid refinement of the compound Ba2Cl2Cu3O4

1995 ◽  
Vol 10 (4) ◽  
pp. 282-287 ◽  
Author(s):  
W. Pitschke ◽  
G. Krabbes ◽  
N. Mattern
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Indexed X-ray powder diffraction data are reported for the semiconducting compound Ba2Cl2Cu3O4. The structure was refined by the Rietveid technique on the basis of the space group I4/mmm. Refined unit cell dimensions are a = 5.5156(1) Å, c = 13.8221(3) Å, V = 420.49 Å3Dx = 4.74 g/cm3, F30 = 129(0.0075,30), M20 = 121, Rp = 6.58, Rwp = 8.66, and RB = 4.49.

Powder Diffraction Data of Potassium Calcium Phosphate KCa PO4.H2O

1987 ◽  
Vol 2 (4) ◽  
pp. 253-254 ◽  
Author(s):  
D. Louër ◽  
F. Deneuve ◽  
N. Ouillon
Keyword(s):  
Calcium Phosphate ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Monoclinic Cell

AbstractPotassium calcium phosphate, KCa PO4.H2O, has been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined from diffractometer data obtained with strictly monochromatized Cu Kα1 radiation, by indexing programs. A C-centered monoclinic cell was found: a =7.5834(9) Å, b = 8.1568(11) Å, c = 7.6541(8) Å, β= 102.975 (9)°.

Indexing Powder Patterns from Relative Axial Dimensions

1990 ◽  
Vol 5 (2) ◽  
pp. 61-63
Author(s):  
Ben Post ◽  
W. Frank McClune
Keyword(s):  
Data Base ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Single Phase ◽  
Unit Cell ◽  
X Ray ◽  
Large Numbers ◽  
Diffraction Patterns ◽  
Goniometric Measurements ◽  
The One

The usefulness of an X-ray powder diffraction data base, such as the one published by the International Centre for Diffraction Data, is largely dependent on continued additions of indexed powder patterns of single-phase materials of interest to data-base users. The single-phase character of a specimen is generally established by using known values of the unit cell constants to index all its powder pattern lines.In this manuscript we describe indexing procedures based on crystal data which provide only relative values of the cell dimensions, rather than the absolute values usually considered to be essential to the indexing process. To the best of our knowledge, the use of such data for indexing powder diffraction patterns has generally been overlooked or ignored by X-ray crystallographers. We refer to the large numbers of goniometric measurements of crystals which have been published both before, and since, the discovery of X-ray diffraction. These provide useful descriptions of chemical and physical properties of crystals as well as measurements of relative dimensions of unit cell axes. The latter are presented in the form of a/b, b/b and c/b, together with the interaxial angle or angles, if the cell is nonorthogonal.

EDIFF: a program for automated unit-cell determination and indexing of electron diffraction data

2011 ◽  
Vol 44 (5) ◽  
pp. 1132-1136 ◽  
Author(s):  
Linhua Jiang ◽  
Dilyana Georgieva ◽  
Jan Pieter Abrahams
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Unit Cell ◽  
Electron Diffraction Data ◽  
Cell Determination ◽  
Diffraction Patterns ◽  
Inorganic Molecules ◽  
User Friendly

EDIFFis a new user-friendly software suite for unit-cell determination of three-dimensional nanocrystals from randomly oriented electron diffraction patterns with unknown independent orientations. It can also be used for three-dimensional cell reconstruction from diffraction tilt series. In neither case is exact knowledge of the angular relationship between the patterns required. The unit cell can be validated and the crystal system assigned.EDIFFcan index the reflections in electron diffraction patterns. Thus,EDIFFcan be employed as a first step in reconstructing the three-dimensional atomic structure of organic and inorganic molecules and of proteins from diffraction data. An example illustrates the viability of theEDIFFapproach.

Sign in / Sign up

Export Citation Format

Share Document