An automated full-symmetry Patterson search method

Rius, Jordi; Miravitlles, C.

doi:10.1107/s0021889887086722

Cited by 24 publications

(16 citation statements)

References 7 publications

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“…Consequently, Patterson search methods were applied. Unlike to direct methods, they can work with low resolution data (Rius, Miravitlles, 1988 (Rius, Miravitlles, 1987), a solution with a reasonably good agreement between observed and calculated intensities for 24 (hOl) reflections (R = 30%) was selected. The corresponding (010) electron density projection shows ring-like arrangements of electron density maxima which are typical of zeolite structures.…”

Section: Solution Of the Structurementioning

confidence: 99%

Ab-initio structure determination of zeolite RUB-10 from low resolution X-ray powder diffraction data

1995

Zeitschrift Für Kristallographie - Crystalline Materials

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The ab-initio solution of the crystal structure of the zeolite material RUB-10 from X-ray powder diffraction data at 2 Â resolution is presented. Microcrystallinity and poor crystallinity are inherent properties of this material that could not be overcome by optimizing the synthesis conditions. RUB-10 is monoclinic with space group P2Ja and a = 13.112(2) Â, b = 12.903(1) Â, c = 12.407(2) Â, ß = 113.50(1)°, V = 1925 Â3, unit cell content: [Si32B4072] [N(CH3)4]4. The general connectivity pattern of the silicate framework which belongs to

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Section: Solution Of the Structurementioning

confidence: 99%

Ab-initio structure determination of zeolite RUB-10 from low resolution X-ray powder diffraction data

1995

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Patterson search methods have been widely used for solving crystal structures from powder data when, as in the present case, only low-resolution intensity data are available (Rius & Miravitlles, 1987). Here, however, the power of these methods is weakened because most integrated intensities are systematically overlapped.…”

Section: Structure Solutionmentioning

confidence: 99%

Phase Transitions in Tris(3,5-dimethylpyrazol-1-yl)methane. The Structure of the High-Temperature Phase from X-ray Powder Diffraction

Ochando¹,

Rius²,

Louër³

et al. 1997

Acta Crystallogr Sect B

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The crystal structure of the sublimated form (m.p. = 424K) of tris(3,5-dimethylpyrazol-l-yl)methane has been solved by a Patterson search method from laboratory X-ray powder diffraction data. Crystal data: trigonal symmetry with the unit-cell parameters a = 16.152(1) and c = 5.353(1)A, space group P3, C16H22N6, Z = 3, 293 K. After indexing the powder pattem by two methods, the unit-cell parameters found were refined by a least-squares technique. A whole pattem-fitting program was used to extract the integrated intensities. The structure was solved taking a related compound as a search model and the final Rietveld refinement converged to Rwp = 0.077 and Rp = 0.059. This study is one of the first examples of Patterson search structure determination from an hemihedral space group using powder data. The complexity of the structural determination is increased by the presence of three molecules in the asymmetric unit.

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“…Finally, we note that knowledge of structural units of well defined geometry has also been exploited in some of the traditional approaches for crystal structure solution from powder diffraction data; particular attention is drawn to model-based Patterson methods (Rius & Miravitlles, 1987, 1988Wilson, 1989;Wilson & Wadsworth, 1990;Cirujeda et al, 1995). However, these fragment-search techniques (unlike the Monte Carlo method) are still intrinsically limited by the requirement to extract the intensities of individual diffraction maxima directly from the powder diffraction pattern.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure Solution from Neutron Powder Diffraction Data by a new Monte Carlo Approach Incorporating Restrained Relaxation of the Molecular Geometry

Tremayne¹,

Kariuki²,

Harris³

et al. 1997

J Appl Cryst

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We report the development of a new aspect of the Monte Carlo method for crystal structure solution from powder diffraction data and demonstrate the advantages of this new approach by applying it to solve the low‐temperature crystal structure (phase II) of perdeuterated pyrene from neutron powder diffraction data. In previous applications of our Monte Carlo technique, the structural fragment was constrained to have a standard geometry throughout the calculation, whereas in the new approach, restrained relaxation of the structural fragment from standard geometry is considered for each structure sampled during the calculation. The new approach gives rise to a substantially improved discrimination (in terms of the weighted profile R factor Rwp) between the correct structure solution and incorrect structures sampled during the Monte Carlo calculation [for the calculation with standard geometry of the structural fragment, Rwp ranged from circa 27.5–30% for `wrong' structures to 21.2% for the best structure solution (i.e. discrimination ~6.3%); for the calculation with relaxation of the geometry of the structural fragment, Rwp ranged from circa 24–26% for `wrong' structures to 11.6% for the best structure solution (i.e. discrimination ~12.4%)]. The work reported here represents the first application of the Monte Carlo method for structure solution using neutron powder diffraction data; the new methodology (applicable to both neutron and X‐ray powder diffraction data) represents a substantial enhancement of the scope and potential of the method, particularly for cases in which the discrimination in Rwp between the correct structure solution and incorrect structure solutions is expected to be inherently small.

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An automated full-symmetry Patterson search method

Cited by 24 publications

References 7 publications

Ab-initio structure determination of zeolite RUB-10 from low resolution X-ray powder diffraction data

Ab-initio structure determination of zeolite RUB-10 from low resolution X-ray powder diffraction data

Phase Transitions in Tris(3,5-dimethylpyrazol-1-yl)methane. The Structure of the High-Temperature Phase from X-ray Powder Diffraction

Crystal Structure Solution from Neutron Powder Diffraction Data by a new Monte Carlo Approach Incorporating Restrained Relaxation of the Molecular Geometry

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