Crystal Structure of La4Si2O7N2Analyzed by the Rietveld Method Using the Time-of-Flight Neutron Powder Diffraction Data

2003 ◽  
Vol 15 (5) ◽  
pp. 1099-1104 ◽  
Author(s):  
Junichi Takahashi ◽  
Hisanori Yamane ◽  
Naoto Hirosaki ◽  
Yoshinobu Yamamoto ◽  
Takayuki Suehiro ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Time Of Flight ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data

Crystal Structure of La4Si2O7N2 Analyzed by the Rietveld Method Using the Time-of-Flight Neutron Powder Diffraction Data.

ChemInform ◽  
2003 ◽  
Vol 34 (22) ◽  
Author(s):  
Junichi Takahashi ◽  
Hisanori Yamane ◽  
Naoto Hirosaki ◽  
Yoshinobu Yamamoto ◽  
Takayuki Suehiro ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Time Of Flight ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data

The crystal structure of perdeuterated methanol monoammoniate (CD3OD·ND3) determined from neutron powder diffraction data at 4.2 and 180 K

2009 ◽  
Vol 42 (6) ◽  
pp. 1054-1061 ◽  
Author(s):  
A. D. Fortes ◽  
I. G. Wood ◽  
K. S. Knight
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Relative Volume ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Neutron Powder Diffraction Data

The crystal structure of perdeuterated methanol monoammoniate, CD3OD·ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180 K. The crystal structure is orthorhombic, space groupPbca(Z= 8), with unit-cell dimensionsa= 11.02320 (7),b= 7.66074 (6),c= 7.59129 (6) Å,V= 641.053 (5) Å3[ρcalc= 1162.782 (9) kg m−3] at 4.2 K, anda= 11.21169 (5),b= 7.74663 (4),c= 7.68077 (5) Å,V= 667.097 (4) Å3[ρcalc= 1117.386 (7) kg m−3] at 180 K. The crystal structure was determined byab initiomethods from the powder data; atomic coordinates and anisotropic displacement parameters were subsequently refined by the Rietveld method toRp< 3% at both temperatures. The crystal comprises a sheet-like structure in thebccrystallographic plane, consisting of strongly hydrogen bonded elements; these sheets are stacked along theaaxis, and adjacent sheets are linked by what may be comparatively weak C—D...O hydrogen bonds. Within the strongly bonded sheet structure, ND3molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule, accepting one hydrogen bond (O—D...N) of length ∼1.75 Å, and donating three hydrogen bonds (N—D...O) of length 2.15–2.25 Å. Two of the methyl deuterons appear to participate in weak interlayer hydrogen bonds (C—D...O) of length 2.7–2.8 Å. The hydrogen bonds are ordered at both 4.2 and 180 K. The relative volume change on warming from 4.2 to 180 K, ΔV/V, is +4.06%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths,e.g.Δa/a) than, that observed in deuterated methanol monohydrate.

The crystal structure of perdeuterated methanol hemiammoniate (CD3OD·0.5ND3) determined from neutron powder diffraction data at 4.2 and 180 K

2010 ◽  
Vol 43 (2) ◽  
pp. 328-336 ◽  
Author(s):  
A. D. Fortes ◽  
I. G. Wood ◽  
K. S. Knight
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Methanol Molecule ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Neutron Powder Diffraction Data

The crystal structure of perdeuterated methanol hemiammoniate, CD3OD·0.5ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180 K. The structure is orthorhombic, space groupPn21a(Z= 4), with unit-cell dimensionsa= 12.70615 (16),b= 8.84589 (9),c= 4.73876 (4) Å,V= 532.623 (8) Å3[ρcalc= 1149.57 (2) kg m−3] at 4.2 K, anda= 12.90413 (16),b= 8.96975 (8),c= 4.79198 (4) Å,V= 554.656 (7) Å3[ρcalc= 1103.90 (1) kg m−3] at 180 K. The crystal structure was determined byab initiomethods from the powder data; atomic coordinates and isotropic displacement parameters were subsequently refined by the Rietveld method toRp≃ 2% at both temperatures. The crystal structure comprises a three-dimensionally hydrogen-bonded network in which the ND3molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule. This connectivity leads to the formation of zigzag chains of ammonia–hydroxy groups extending along thecaxis, formedviaN—D···O hydrogen bonds; these chains are cross-linked along theaaxis through the hydroxy moiety of the second methanol moleculeviaN—D···O and O—D···O hydrogen bonds. This `bridging' hydroxy group in turn donates an O—D···N hydrogen bond to ammonia in adjacent chains stacked along thebaxis. The methyl deuterons in methanol hemiammoniate, unlike those in methanol monoammoniate, do not participate in hydrogen bonding and reveal evidence of orientational disorder at 180 K. The relative volume change on warming from 4.2 to 180 K, ΔV/V, is + 4.14%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths,e.g.Δa/a) than, that observed in deuterated methanol monohydrate, and very similar to what is observed in methanol monoammoniate.

Determination and Rietveld refinement of the crystal structure of Li0.50Ni0.25TiO(PO4) from powder X-ray and neutron diffraction

2002 ◽  
Vol 17 (4) ◽  
pp. 290-294 ◽  
Author(s):  
B. Manoun ◽  
A. El Jazouli ◽  
P. Gravereau ◽  
J. P. Chaminade ◽  
F. Bouree
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Monoclinic Cell

The structure of the oxyphosphate Li0.50Ni0.25TiO(PO4) has been determined from conventional X-ray and neutron powder diffraction data. The parameters of the monoclinic cell (space group P21/c, Z=4), obtained from X-ray results, are: a=6.3954(6) Å, b=7.2599(6) Å, c=7.3700(5) Å, and β=90.266(6)°; those resulting from neutron study are: a=6.3906(7) Å, b=7.2568(7) Å, c=7.3673(9) Å, and β=90.234(7)°. Refinement by the Rietveld method using whole profile, leads to satisfactory reliability factors: cRwp=0.128, cRp=0.100, and RB=0.038 for X-ray and cRwp=0.110, cRp=0.120, and RB=0.060 for neutrons. The structure of Li0.50Ni0.25TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis and cross linked by phosphate tetrahedra. In this framework, there are octahedral cavities occupied by Li and Ni atoms: Li occupies the totality of the 2a sites and Ni occupies statistically half of the 2b sites. Ti atoms are displaced from the center of octahedra units in alternating long (2.242 Å) and short (1.711 Å) Ti–O bonds along chains.

On the numerical corrections of time-of-flight neutron powder diffraction data

2007 ◽  
Vol 40 (4) ◽  
pp. 710-715 ◽  
Author(s):  
Maxim Avdeev ◽  
James Jorgensen ◽  
Simine Short ◽  
Robert B. Von Dreele
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Time Of Flight ◽  
Wavelength Dependence ◽  
Rietveld Analysis ◽  
Neutron Powder Diffraction ◽  
Standard Reference Materials ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data ◽  
Voigt Function

Time-of-flight neutron powder diffraction data for NIST Standard Reference Materials have been used to study the adequacy of the peak profile model obtained from a convolution of back-to-back exponentials with a pseudo-Voigt function that is widely used in Rietveld refinement. It is shown that, while the empirical models ford-spacing (wavelength) dependence of Gaussian and Lorentzian components of the pseudo-Voigt function and rise exponent are satisfactory, the behavior of the decay exponent and peak positions demonstrate significant deviations, which can be corrected by numerical methods. The practical side of this process as implemented inGSASandFULLPROFand the effect of the corrections on the Rietveld analysis results are discussed.

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