scholarly journals Application of Charge & Band-flipping to Time-of-Flight Neutron Diffraction Data

2014 ◽  
Vol 70 (a1) ◽  
pp. C188-C188 ◽  
Author(s):  
Pamela Whitfield ◽  
Alan Coehlo ◽  
Ashfia Huq ◽  
Christina Hoffmann ◽  
Xiaoping Wang
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Time Of Flight ◽  
Easy Access ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Neutron Data

Charge-flipping has become a popular approach to ab-initio structure solution from X-ray powder diffraction data in particular due to its speed and need for minimal input other than lattice parameters. Given the appetite of charge-flipping for low d-spacing reflections, time-of-flight (TOF) neutron data should be a good match from a resolution standpoint, with easy access to high Q and lack of form-factor drop-off. One obvious issue with neutron data is the presence of elements with negative scattering lengths, where the inherent assumption of atoms always having positive `density' in the algorithm breaks down. This means that portions of the structure can be effectively invisible. Given that some of these elements (e.g. H and Mn) are commonly found in samples of interest the issue is more than simple academic curiosity. Of course such atoms can be found by difference maps, but the issue has also been addressed within the charge-flipping algorithm with the `band-flipping' modification [1]. Although Oszlányi & Sütö demonstrated the approach was viable with simulated neutron single crystal data [1], to the authors' knowledge it hasn't been used previously with experimental single crystal or powder neutron diffraction data. Powder diffraction data from POWGEN and wavelength-resolved TOF Laue single crystal data from TOPAZ at the Spallation Neutron Source have been used to probe the relative ease of charge-flipping with different TOF data using the TOPAS software package [2]. In addition the effectiveness of different customized band-flipping approaches has been tested to extract positions for positive and negative scattering elements simultaneously.

Crystal Data for [Cu(C15H11N3)X2]·nH2O [X−=NCO (n=1); NCSe and N3 (n=ø)] Compounds

1989 ◽  
Vol 4 (3) ◽  
pp. 162-164
Author(s):  
J. Vía ◽  
A. García ◽  
J. L. Mesa ◽  
M. I. Arriortua ◽  
T. Rojo
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
The Family ◽  
Reaction In Solution

AbstractThree members of the family [CuC15H11N3)X2]·nH2O [X−=NCO (n=1), NCSe and N3 (n=ø)], C15H11N3=2,2′:6′,2″ – terpyridine (terpy), have been prepared by reaction in solution. Crystal data determined widi the aid of single crystal methods, powder diffraction data, and densities determined by flotation methods are presented.

Structure of Ce2Pt6Ga15: interplanar disorder from the Ce2Ga3 layers

1996 ◽  
Vol 52 (4) ◽  
pp. 580-585 ◽  
Author(s):  
G. H. Kwei ◽  
A. C. Lawson ◽  
A. C. Larson ◽  
B. Morosin ◽  
E. M. Larson ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Diffuse Scattering ◽  
Heavy Fermion ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
A Cell

The structure of the heavy fermion compound Ce2Pt6Ga15 has been determined from neutron powder and X-ray/neutron single-crystal diffraction. Examination of symmetry equivalence among the single-crystal data, as well as the good fit of the powder data to the final structural arrangement, with all the atoms on symmetry sites, suggests that the correct space group is P63/mmc. The structure is unusual in that Ce layers have 1/3 of the Ce atoms replaced by groups of three Ga atoms; distances between atoms in these planes suggest this substitution must occur in a concerted fashion. The refined occupancies lead to a stoichiometry near Ce2Pt6Ga15, consistent with such an arrangement. In addition, single-crystal neutron diffraction data show columns of weak diffuse scattering along the <001> axes, suggesting disorder arising from a lack of registration of successive Ce2Ga3 layers (lying half a cell length or 8.27 Å apart along z) and a 3 × 3 × 1 supercell. This disorder is very likely responsible for the low resistance ratio of approximately unity measured for single-crystal samples.

Crystal data of the low-temperature solid form of 2-methyl-2-nitro-propanol(MNP)

1994 ◽  
Vol 9 (2) ◽  
pp. 84-86 ◽  
Author(s):  
J. Ll. Tamarit ◽  
N. B. Chanh ◽  
P. Négrier ◽  
D. O. López ◽  
M. Barrio ◽  
...  
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Type Space ◽  
Solid Form

By means of X-ray single crystal Weissenberg photographs, the crystal of the low-temperature solid form of 2-methyl-2-nitro-propanol, (CH3)2C(NO2)(CH2OH), has been determined and found to be of the monoclinic type, space group P21/c. The cell constants were refined from X-ray powder diffraction data: a=6.195(3) Å, b=19.116(7) Å, c=16.598(7) Å, and β = 90.12(2)° with Z = 12. The indexed pattern at 293 K is given.

Solving the Crystal Structure of Cd5(OH)8(NO3)2·2H2O from Powder Diffraction Data. A Comparison with Single Crystal Data

1991 ◽  
Vol 6 (1) ◽  
pp. 10-15 ◽  
Author(s):  
Patricia Bénard ◽  
Michèle Louër ◽  
Daniel Louër
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Subsequent Treatment ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Indexing Method ◽  
Parameter Values

AbstractA comparison between the results of ab initio structure determination from X-ray powder diffraction data of a new cadmium hydroxide nitrate, Cd5(OH)8 (NO3)2·2H2O (SG C2/m), and those obtained from single crystal data is presented. The powder diffraction pattern has been analysed by an indexing method and fitting techniques. A total of 119 unambiguously indexed reflections has been extracted and used in subsequent treatment. The power of powder techniques to index the pattern and to find the structure model by normal Patterson and Fourier methods is clearly shown. The refinement of approximate coordinates has been carried out by the Rietveld method (444 reflections). The comparison of results with those obtained from single crystal data (2218 reflections) shows that the precision of positional parameter values is lower by a factor of 10, on average, in the powder study. These results are discussed in terms of crystallographic parameters (number of reflections used, number of parameters to refine, contrast between atoms) and, also, in terms of sample dependent properties (preferred orientation effect, impurity). Finally, the crystal structure has been derived from powder data with a precision probably sufficient for most purposes.

Crystal data for [Cu(LIII)XY]·nH2O compounds [LIII=pymep, terpy; X=I, N3; Y=I, NO3, PF6; n=0,1]

1994 ◽  
Vol 9 (3) ◽  
pp. 161-163
Author(s):  
M. I. Arriortua ◽  
M. Insausti ◽  
R. Cortès ◽  
J. I. R. Larramendi
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Flotation Method ◽  
New Compounds ◽  
Reaction In Solution

Three new compounds of generalised formula [Cu(LIII)XY]·nH2O [LIII=pymep, terpy; X=I, N3; Y=I, NO3, PF6; n=0,1], pymep (C14H15N3)=N-(6methyl–2-pyridyl–methylene) -2-(2-pyridyl)-ethylamine and terpy (C15H11N3)=2,2′;6′,2″-terpyridine have been prepared by reaction in solution. Crystal data were determined by single-crystal methods. Powder diffraction data and densities determined by a flotation method are also presented.

Hereroite and vladkrivovichevite: two novel lead oxychlorides from the Kombat mine, Namibia

2012 ◽  
Vol 76 (4) ◽  
pp. 883-890 ◽  
Author(s):  
R. Turner ◽  
O. I. Siidra ◽  
M. S. Rumsey ◽  
S. V. Krivovichev ◽  
C. J. Stanley ◽  
...  
Keyword(s):  
Single Crystal ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Calculated Density ◽  
X Ray ◽  
Conchoidal Fracture ◽  
The Mean

AbstractTwo new lead oxychloride minerals, hereroite [Pb32(O, ☐)21](AsO4)2((Si,As,V,Mo)O4)2Cl10 and vladkrivovichevite [Pb32O18][Pb4Mn2O]Cl14(BO3)8·2H2O occur in association with asisite, damaraite, kombatite, sahlinite, copper, quartz, barysilite, Mn silicates and a number of Mn oxyhydroxide minerals on a specimen from the Kombat mine in Namibia. The minerals formed as late-stage products of hydrothermal reworking of primary sulfide minerals.Hereroite is monoclinic, C2/c with a = 23.14(1), b = 22.65(1), c = 12.39(1) Å, β = 102.00(5)°, V = 6351.6(41) Å3 from powder-diffraction data and a = 23.139(4), b = 22.684(4), c = 12.389(2) Å, β = 102.090(3)°, V = 6358.8(18) Å3 from single-crystal data. It is bright orange, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 8.15 g cm–3. The mean refractive index in air at 589 nm is 2.38. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.982(100)(51); 2.795(47)(80); 1.986(24)(8); 1.641(24)(11..); 3.512(23)(61); 3.901(21)(511). Hereroite is named for the Herero people, one of the indigenous tribal groupings in the region where the Kombat mine is located.Vladkrivovichevite is orthorhombic, Pmmn with a = 12.87(5), b = 27.7(4), c = 11.46(3) Å, V = 4080.1(5) Å3, from powder-diffraction data and a = 12.759(1), b = 27.169(4), c = 11.515(1) Å, V = 3992.0(9) Å3, Z = 2, from single-crystal data. It is pale greenish yellow, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 7.40 g cm–3. The mean refractive indices in air at 589 nm are 2.30 and 2.34. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.860(100)(370); 2.733(84)(073); 3.707(49)(073); 3.068(37)(401); 2.075(32)(473); 1.601(32)(3.14.3). Vladkrivovichevite is named in honour of Prof. Dr Vladimir Gerasimovich Krivovichev (b. 24.04.1946), Head of the Department of Mineralogy, Geological Faculty, St Petersburg State University.The crystal structures of hereroite and vladkrivovichevite consist of alternating litharge-like O – Pb double layers and chlorine sheets and both are structurally related to other layered lead oxychlorides. In hereroite, tetrahedral AsO4 and (Si, As, V, Mo)O4 groups locate in defects within the O – Pb block, which combines square 'symesite-type' and double-square 'kombatite-type' cavities in its crystal structure. The structure of vladkrivovichevite is based on O – Pb derivative blocks with the interlayer occupied by Cl– anions and oxocentred OPb4Mn2 octahedra whose eight triangular faces are capped by triangular borate anions, BO33–.

Powder X-ray diffraction data of BaFI

2000 ◽  
Vol 15 (2) ◽  
pp. 130-133 ◽  
Author(s):  
N. Subramanian ◽  
N. V. Chandra Shekar ◽  
P. Ch. Sahu ◽  
Mohammad Yousuf ◽  
K. Govinda Rajan
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Atmospheric Pressure ◽  
Calculated Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Standard Temperature ◽  
X Ray

This paper presents the powder X-ray diffraction data of BaFI recorded using a Guinier diffractometer and Mo Kα1 radiation. BaFI stabilizes at standard temperature of 25 °C and standard-atmospheric pressure (STP) in the tetragonal structure (space group P4/nmm; No. 129) with lattice parameters a=4.660(1) Å and c=7.960(5) Å. Our observed pattern is different from the existing observed powder diffraction data reported in the PDF files 34-716 (Beck, 1976) and 31-139 (), but matches almost perfectly with the pattern calculated by us from the reported single crystal data ( and with the calculated data available in PDF file 70-0481. Further, our data provide a number of new Bragg peaks extending beyond the range of d values available in the existing PDF files.

Crystal Data for Pb7Bi3, a Superconducting ε-Phase in the Pb-Bi System

1987 ◽  
Vol 2 (1) ◽  
pp. 28-28 ◽  
Author(s):  
Svend Erik Rasmussen ◽  
Britta Lundtoft
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Superconducting State ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Space Group ◽  
X Ray ◽  
Crystal Material ◽  
Ε Phase

AbstractThe ε-phase is hexagonal, space group P63/mmc. For the composition Pb7Bi3 the following data were determined, a = 3.5058(1) Å c = 5.7959(5) Å, Vol. = 61.687 Å3(5), Dc = 11.17 Mg m−3. Filings from single crystal material were used to obtain powder data by the Guinier method and the X-ray results were in accordance with single crystal neutron diffraction data. Transition to the superconducting state took place in the interval 8.3 K–8.55 K.

Crystal Data for [Cu(C14H15N3)X2·nH2O [X = N3 (n = 1); NCS and Br (n = 0)] Compounds

1991 ◽  
Vol 6 (1) ◽  
pp. 40-42
Author(s):  
M.I. Arriortua ◽  
J. Vía ◽  
J.I.R. Larramendi ◽  
T. Rojo
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
The Family ◽  
Reaction In Solution

AbstractThree members of the family [Cu(C14H15N3)X2]·nH2O [X = N3(n = 1); NCS and Br(n = 0)], C14H15N3, = N-(2′-(6-methyl) pyridyl) methylene-2-(2′-pyridyl)ethylamine)] (pymep), have been prepared by reaction in solution. Crystal data determined with the aid of single crystal methods, powder diffraction data, and densities determined by flotation methods are presented.

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