<i>EXPO</i>: a program for full powder pattern decomposition and crystal structure solution

Altomare, Angela; Burla, Maria Cristina; Camalli, Mercedes; Carrozzini, Benedetta; Cascarano, G.; Giacovazzo, Carmelo; Guagliardi, Antonietta; Moliterni, Anna; Polidori, Giampiero; Rizzi, Rosanna

doi:10.1107/s0021889898007729

Cited by 478 publications

(304 citation statements)

References 9 publications

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“…The indexing of the diffraction pattern of Mu-9 had proven to be difficult, because there appeared to be an unidentified impurity in the sample. Attempts to solve the structure assuming several possible unit cells and space groups using the direct methods program EXPO [24] and the zeolite-specific program Focus [25] had failed. The presence of an impurity not only made indexing difficult, but also made an accurate chemical analysis impossible and the interpretation of 27 Al, 31 P and 13 C MAS NMR results uncertain.…”

Section: Examplesmentioning

confidence: 99%

Exploiting texture to estimate the relative intensities of overlapping reflections

Baerlocher¹,

McCusker²,

Prokic³

et al. 2004

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract. Additional information about the relative intensities of reflections that overlap in a powder diffraction pattern can be obtained from a polycrystalline sample in which the crystallites are preferentially oriented. If the data are collected and analyzed appropriately, more single-crystal-like reflection intensities can be extracted, and thereby more complex structures solved. This 'texture method' was implemented initially in reflection mode and its power demonstrated with the solution of the 117-atom structure of the high-silica zeolite UTD-1F. However, the experiment required a minimum of 3 days of synchrotron beamtime per sample. In an attempt to reduce the amount of beamtime needed and to simplify the experiment itself, a transmission mode alternative using an area detector was developed. Details of the sample preparation, data collection and data analysis for both geometries are described. The solution of the structures of the aluminophosphates Mu-9 (R 3 3c, a ¼ 14.0696(1) A, c ¼ 42.3113(4) A) and AlPO-M (Pbca, a ¼ 9.7493(1) A, b ¼ 29.1668(2) A, c ¼ 9.3528(1) A) using reflection and transmission mode data, respectively, are provided as examples of the method.

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Section: Examplesmentioning

confidence: 99%

Exploiting texture to estimate the relative intensities of overlapping reflections

Baerlocher¹,

McCusker²,

Prokic³

et al. 2004

Zeitschrift Für Kristallographie - Crystalline Materials

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“…However, the program did not detect the solution automatically since the drop in R-value was too small. Again several jobs were run, and in the ED maps from runs with the lowest R-value, all atoms were well re- The structure of the zirconium phosphate ZrPOF-pyr (Dong et al, 2006, Pnnm, a ¼ 19.168 A, b ¼ 15.145 A, c ¼ 6.621 A; 29 non-H atoms in the asymmetric unit and 126 in the unit cell) had been solved by direct methods using the program EXPO (Altomare et al, 1999) from synchrotron data (SNBL, ESRF, Grenoble, l ¼ 0.80062 A), but some disorder in one of the phosphate groups was apparent. Attempts to refine an ordered structure in lower space groups had not improved the fit, so it was of interest to see if the charge flipping approach would reveal a different symmetry.…”

Section: Zsm-5 ([Si 96 O 192 ])mentioning

confidence: 99%

Charge flipping combined with histogram matching to solve complex crystal structures from powder diffraction data

Baerlocher¹,

McCusker²,

Palatinus³

2007

Zeitschrift Für Kristallographie

131

107

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Abstract. The charge-flipping structure-solution algorithm introduced by Oszlányi and Sütő in 2004 has been adapted to accommodate powder diffraction data. In particular, a routine for repartitioning the intensities of overlapping reflections has been implemented within the iterative procedure. This is done by modifiying the electron density map with a histogram-matching algorithm, and then using the Fourier coefficients obtained from this map to repartition the structure factor amplitudes within each overlap group. The effectiveness of the algorithm has been demonstrated with five test examples covering different classes of materials of varying complexity ]), cimetidine (C 10

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“…The crystal structure of Sr 3 P 6 O 6 N 8 was solved on the basis of powder X-ray diffraction data by direct methods (EXPO) 25 and refined by the Rietveld method (GSAS;…”

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confidence: 99%

Sr3P6O6N8—a highly condensed layered phosphate

2009

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We describe the synthesis and the structure elucidation of Sr 3 P 6 O 6 N 8 , a novel, highly condensed layered phosphate.During the last decades, inorganic phosphates have emerged from chemical commodities to advanced materials. Classical application areas of these basic inorganic compounds include usage as water softeners, fertilizers and coating materials.1 Nowadays, phosphates are being used as ionic conductors, 2 catalysts in organic syntheses 3 and even as modern optical materials. The structural chemistry of inorganic phosphates has been widely studied in the past.7 Classical representatives consist predominantly of orthophosphates, finite and infinite chainphosphates, as well as ring-phosphates. Here Q 0 (non-linking) up to Q 2 -type (double linking) PO 4 -tetrahedra occur. Band-, layer-or framework-structures with Q 3 or even Q 4 -type tetrahedra (comparable to silicates) have barely been identified. For higher condensed phosphates (exhibiting a degree of condensation (i.e. the molar ratio P : O = k > 1/3)), only a few examples in the group of ultraphosphates have been described. Moreover, the maximum degree of condensation for oxophosphates is k = 0.40. 8A further increase of cross-linking in phosphates, and thereby higher condensed structures, can be achieved in nitridophosphates or oxonitridophosphates by full or partial substitution O/N. With the integration of three-fold linking nitrogen, the structural diversity is significantly enhanced resulting in silicateanalogous networks, the latter being a consequence of the isolobal relation between P-N and Si-O which is further corroborated, for example, by HPN 2 (= PN(NH)) and PON that are isosteric to SiO 2 . By variation of the molar ratio O : N, thus changing the framework charge, network structures with different topologies similar to silicate structures can be achieved. Complete substitution of O for N, yields nitridophosphates like MP 4 N 7 with M = K, Rb, Cs 9 which adopt a network of corner-sharing PN 4 -tetrahedra. The silicate analogy has further been demonstrated by the class of nitridosodalites 10 and related oxonitridosodalites. 11However, complementing the diverse and rich structural chemistry of oxosilicates, new framework-types have been realized in (oxo-)nitridophosphates, 12 e.g. the first nitridic zeolite NPO. 13Department of Chemistry and Biochemistry, Ludwig-MaximiliansUniversität, Butenandtstrasse 5-13, 81377, Munich, Germany. E-mail: wolfgang.schnick@uni-muenchen.de; Fax: +49 89 Recently, this novel framework-type containing large 12-ring channels was paralleled by its nitridosilicate analogue.14 Another novel porous compound was obtained under high-pressure conditions-P 4 N 4 (NH) 4 (NH 3 )15 -the first nitridic clathrate that traps ammonia molecules in an unique cage structure that had been previously predicted as a possible silica framework.16,17 Highly condensed layer structures had not been realized so far; this includes oxophosphates and nitridophosphates, although the layered O¢-form of (P 2 O 5 ) x was discovered in the ...

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EXPO: a program for full powder pattern decomposition and crystal structure solution

Cited by 478 publications

References 9 publications

Exploiting texture to estimate the relative intensities of overlapping reflections

Exploiting texture to estimate the relative intensities of overlapping reflections

Charge flipping combined with histogram matching to solve complex crystal structures from powder diffraction data

Sr3P6O6N8—a highly condensed layered phosphate

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