Ab initio solution of a complex crystal structure from powder-diffraction data using simulated-annealing method and a high degree of molecular flexibility

1997 ◽  
Vol 55 (18) ◽  
pp. 12011-12017 ◽  
Author(s):  
Yuri G. Andreev ◽  
Graham S. MacGlashan ◽  
Peter G. Bruce
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Complex Crystal Structure ◽  
High Degree ◽  
Complex Crystal ◽  
Annealing Method

scholarly journals Crystal structure of Pigment Red 254 from X-ray powder diffraction data

2017 ◽  
Vol 73 (4) ◽  
pp. 507-510 ◽  
Author(s):  
Svetlana N. Ivashevskaya
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Pyrrole Ring ◽  
Inversion Center ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Unique Part ◽  
Low Solubility ◽  
Annealing Method

The crystal structure of Pigment Red 254 [P.R. 254, C18H10Cl2N2O2; systematic name: 3,6-bis(4-chlorophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione] was solved from laboratory X-ray powder diffraction data using the simulated annealing method followed by Rietveld refinement because the very low solubility of the pigment in all solvents impedes the growth of single crystals suitable for X-ray analysis. The molecule lies across an inversion center. The dihedral angle between the benzene ring and the pyrrole ring in the unique part of the molecule is 11.1 (2)°. In the crystal, molecules are linkedviaN—H...O hydrogen bonds, forming chains along [110] incorporatingR22(8) rings.

Ab initio structure determination of In2H2(P2O7)(P4O12) from X-ray powder diffraction data

2003 ◽  
Vol 218 (1) ◽  
Author(s):  
L. S. Ivashkevich ◽  
A. S. Lyakhov ◽  
A. F. Selevich ◽  
A. I. Lesnikovich
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Ab Initio Structure

AbstractThe crystal structure of In

Molecular, crystallographic and algorithmic factors in structure determination from powder diffraction data by simulated annealing

2002 ◽  
Vol 35 (4) ◽  
pp. 443-454 ◽  
Author(s):  
Kenneth Shankland ◽  
Lorraine McBride ◽  
William I. F. David ◽  
Norman Shankland ◽  
Gerald Steele
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Solution Process ◽  
Search Space ◽  
Systematic Investigation ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
Structure Solution

The crystal structure of famotidine form B has been solved directly from powder diffraction data by the application of simulated annealing. The molecule crystallizes in the monoclinic space groupP21/cwith refined unit-cell dimensionsa = 17.6547 (4),b= 5.2932 (1),c= 18.2590 (3) Å and β = 123.558 (1)° atT= 130 K. The core of this work is a systematic investigation of the influence of algorithmic, crystallographic and molecular factors on the structure solution process. With an appropriate choice of annealing schedule, molecular description and diffraction data range, the overall number of successes in solving the crystal structure is close to 100%. Other factors, including crystallographic search space restrictions and parameter sampling method, have little effect on the structure solution process. The basic principles elucidated here have been factored into the design of theDASHstructure solution program.

Ab initio determination and Rietveld refinement of the crystal structure of Ni0.50TiO(PO4)

1999 ◽  
Vol 14 (1) ◽  
pp. 10-15 ◽  
Author(s):  
P. Gravereau ◽  
J. P. Chaminade ◽  
B. Manoun ◽  
S. Krimi ◽  
A. El Jazouli
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Heavy Atom ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Heavy Atom Method

The structure of the oxyphosphate Ni0.50TiO(PO4) has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is monoclinic (space group P21/c, Z=4) with a=7.3830(5) Å, b=7.3226(5) Å, c=7.3444(5) Å, and β=120.233(6)°. Refinement of 46 parameters by the Rietveld method, using 645 reflexions, leads to cRwp=0.152, cRp=0.120, and RB=0.043. The structure of Ni0.50TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis, crosslinked by phosphate tetrahedra and in which one-half of octahedral cavities created are occupied by Ni atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.231) and short (1.703 Å) Ti–O bonds along chains.

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