Hydrogen atoms location in [Re4(µ3-H)4(CO)12] by joint X-ray single-crystal and neutron powder diffraction analysis

1997 ◽  
pp. 1903 ◽  
Author(s):  
Norberto Masciocchi ◽  
Angelo Sironi ◽  
Norberto Masciocchi ◽  
Giuseppe D’Alfonso ◽  
Winfried Kockelmann ◽  
...  
Keyword(s):  
Single Crystal ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Hydrogen Atoms ◽  
X Ray

scholarly journals Neutron powder diffraction analysis of guanosine dihydrate using MEM

2014 ◽  
Vol 70 (a1) ◽  
pp. C1573-C1573
Author(s):  
Yoko Sugawara ◽  
Shigefumi Yamamura ◽  
Akinori Hoshikawa ◽  
Toru Ishigaki ◽  
Takashi Kamiyama
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Neutron Powder Diffraction Data

In majority of the crystals of pharmaceutical compounds, hydrogen bonds play a crucial role. Determination of a hydrogen position is highly important, in order to investigate hydrogen bonds especially in the case of hydrates. We have been investigating humidity-induced phase transitions of hydrates systematically [1,2]. Unique characteristics of hydration water molecules have prompted us to explore the phenomena more precisely. Neutron diffraction analysis is a powerful tool to determine hydrogen positions. However, large single crystals are required because of weak neutron diffraction intensities. Under such background, we carried out neutron powder diffraction analysis of guanosine dihydrate using the Maximum Entropy Method (MEM). Neutron powder diffraction data of guanosine dihydrate (C10H13N5O5.2H2O; crystal data: monoclinic, space group P21, a = 17.518, b = 11.278, c = 6.658 Å, β= 98.170, Z = 4) were measured by iMATERIA at MLF in J-PARC (Figure 1(a)). Rietveld analysis was carried out using atomic coordinates of non-hydrogen atoms determined by X-ray analysis and those of hydrogen atoms which were placed on the geometrically calculated positions using the averaged X-H bond lengths determined by neutron analysis referencing the hydrogen positions estimated by X-ray analysis. Using Fo and σ by Rietveld analysis, the nuclear density distribution was calculated by MEM (Figure 1(b)). Nuclear densities of the hydrogen atoms of one water molecule (W1 in Figure 1) were elongated, which is consistent with the results of molecular dynamic simulation [2]. The effective usage of MEM to elucidate hydrogen atom positions from neutron powder diffraction data will be discussed together with that of difference Fourier calculations.

scholarly journals The growth of Mg2TiO4 single crystals using a four-mirror furnace

2011 ◽  
Vol 76 (11) ◽  
pp. 1561-1566 ◽  
Author(s):  
Aleksandar Golubovic ◽  
Marko Radovic
Keyword(s):  
Optical Properties ◽  
Single Crystal ◽  
Diffraction Analysis ◽  
Single Crystals ◽  
Powder Diffraction ◽  
Spectroscopic Ellipsometry ◽  
Lattice Parameter ◽  
Published Data ◽  
X Ray ◽  
Float Zone

A single crystal of Mg2TiO4 was grown by the travelling solvent float zone (TSFZ) method. The lattice parameter a = 0.8444(8) nm was determined by X-ray powder diffraction analysis. The optical properties of the Mg2TiO4 single crystals were studied using spectroscopic ellipsometry. The obtained results are discussed and compared with published data.

scholarly journals Single-crystal X-ray and neutron powder diffraction investigation of the phase transition in tetrachlorobenzene

2006 ◽  
Vol 62 (2) ◽  
pp. 287-295 ◽  
Author(s):  
Sarah A. Barnett ◽  
Charlotte K. Broder ◽  
Kenneth Shankland ◽  
William I. F. David ◽  
Richard M. Ibberson ◽  
...  
Keyword(s):  
Phase Transition ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Structural Changes ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Polymorphic Phase Transition ◽  
X Ray ◽  
Apparent Loss ◽  
Two Phases

The polymorphic phase transition of 1,2,4,5-tetrachlorobenzene (TCB) has been investigated using neutron powder diffraction and single-crystal X-ray diffraction. The diffraction experiments show a reversible phase change that occurs as a function of temperature with no apparent loss of sample quality on transition between the two phases. Neutron powder diffraction gives detailed information on the molecular structural changes and lattice parameters from 2 K to room temperature. The structure of the low-temperature form has been elucidated for the first time using single-crystal X-ray diffraction. Comparison of the α and β structures show that they are both based on the same sheet motif, with the differences between the two being very subtle, except in terms of crystal symmetry. Detailed analysis of the structures revealed the changes required for inter-conversion. A computational polymorph search showed that these two sheet structures are more thermodynamically stable than alternative herringbone-type structures.

X-ray powder diffraction analysis of tegafur

2006 ◽  
Vol 21 (3) ◽  
pp. 245-247 ◽  
Author(s):  
F. Needham ◽  
J. Faber ◽  
T. G. Fawcett ◽  
D. H. Olson
Keyword(s):  
Single Crystal ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Antineoplastic Agent ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Cell Parameters ◽  
Structural Database

An experimental X-ray powder diffraction pattern was produced and analyzed for alpha-polymorphic tegafur, also called Ftorafur (an antineoplastic agent). The indexed data matched the powder patterns in the ICDD PDF-4/Organics database calculated from the reported single-crystal X-ray diffraction data in the Cambridge Structural Database. Alpha tegafur has a triclinic crystal system, with reduced cell parameters of a=16.720(6) Å, b=9.021(5) Å, c=5.995(3) Å, α=93.66(4)°, β=93.15(8)°, γ=100.14(4)°. There are four formula units contained in one unit cell. The cell volume and space group were determined to be 886.27 Å3 and P-1, respectively.

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