Crystal structures and new perspectives on Y3Au4 and Y14Au51

2017 ◽  
Vol 73 (9) ◽  
pp. 692-696 ◽  
Author(s):  
Chris Celania ◽  
Volodymyr Smetana ◽  
Anja-Verena Mudring
Keyword(s):  
Rare Earth ◽  
Crystal Structures ◽  
Structure Type ◽  
Unit Cell ◽  
Tunnel Structure ◽  
Unit Cell Parameters ◽  
Rare Earth Atom ◽  
Space Groups ◽  
Cell Parameters ◽  
Group 12

Y3Au4 (triyttrium tetragold) and Y14Au51 (tetradecayttrium henpentacontagold), two binary representatives of Au-rich rare earth (R) systems crystallize with the space groups R\overline{3} and P6/m, adopting the Pu3Pd4 and Gd14Ag51 structure types, respectively (Pearson symbols hR42 and hP65). A variety of binary R–Au compounds have been reported, although only a few have been investigated thoroughly. Many reports lack information or misinterpret known compounds reported elsewhere. The Pu3Pd4 type is fairly common for group 10 elements Ni, Pd, and Pt, while Au representatives are restricted to just five examples, i.e. Ca3Au4, Pr3Au4, Nd3Au4, Gd3Au4, and Th3Au4. Sm6Au7 is suspected to be Sm3Au4 due to identical symmetry and close unit-cell parameters. The Pu3Pd4 structure type allows for full substitution of the position of the rare earth atom by more electronegative and smaller elements, i.e. Ti and Zr. The Gd14Ag51 type instead is more common for the group 11 metals, while rare representatives of group 12 are known. Y3Au4 can be represented as a tunnel structure with encapsulated cations and anionic chains. Though tunnels are present in Y14Au51, this structure is more complex and is best described in terms of polyhedral `pinwheels' around the tunnel forming polyhedra along the c axis.

The structures of marialite (Me6) and meionite (Me93) in space groups P42/n and I4/m, and the absence of phase transitions in the scapolite series

2011 ◽  
Vol 26 (2) ◽  
pp. 119-125 ◽  
Author(s):  
Sytle M. Antao ◽  
Ishmael Hassan
Keyword(s):  
Phase Transitions ◽  
High Resolution ◽  
Crystal Structures ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Space Groups ◽  
Cell Parameters ◽  
The Mean

The crystal structures of marialite (Me6) from Badakhshan, Afghanistan and meionite (Me93) from Mt. Vesuvius, Italy were obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Their structures were refined in space groups I4/m and P42/n, and similar results were obtained. The Me6 sample has a formula Ca0.24Na3.37K0.24[Al3.16Si8.84O24]Cl0.84(CO3)0.15, and its unit-cell parameters are a=12.047555(7), c=7.563210(6) Å, and V=1097.751(1) Å3. The average ⟨T1-O⟩ distances are 1.599(1) Å in I4/m and 1.600(2) Å in P42/n, indicating that the T1 site contains only Si atoms. In P42/n, the average distances of ⟨T2-O⟩=1.655(2) and ⟨T3-O⟩=1.664(2) Å are distinct and are not equal to each other. However, the mean ⟨T2,3-O⟩=1.659(2) Å in P42/n and is identical to the ⟨T2′-O⟩=1.659(1) Å in I4/m. The ⟨M-O⟩ [7]=2.754(1) Å (M site is coordinated to seven framework O atoms) and M-A=2.914(1) Å; these distances are identical in both space groups. The Me93 sample has a formula of Na0.29Ca3.76[Al5.54Si6.46O24]Cl0.05(SO4)0.02(CO3)0.93, and its unit-cell parameters are a=12.19882(1), c=7.576954(8) Å, and V=1127.535(2) Å3. A similar examination of the Me93 sample also shows that both space groups give similar results; however, the C–O distance is more reasonable in P42/n than in I4/m. Refining the scapolite structure near Me0 or Me100 in I4/m forces the T2 and T3 sites (both with multiplicity 8 in P42/n) to be equivalent and form the T2′ site (with multiplicity 16 in I4/m), but ⟨T2-O⟩ is not equal to ⟨T3-O⟩ in P42/n. Using different space groups for different regions across the series implies phase transitions, which do not occur in the scapolite series.

Crystal structure of three diaza-crowns-18

1997 ◽  
Vol 212 (5) ◽  
Author(s):  
P. Dokurno ◽  
R. Trokowski ◽  
B. Kościuszko-Panek ◽  
T. Ossowski ◽  
A. Konitz ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Groups ◽  
Cell Parameters

AbstractThe crystal structures of three diaza crowns-18, namely 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (crown 1), 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diacetonitrile (crown 2) and N,N′-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyldi-2,1-ethanediyl)bis-[4-methyl-benzenesulfonamide] (crown 3) have the following space groups and unit cell parameters: crown 1(C

scholarly journals Crystal structures and comparisons of potassium rare-earth molybdates KRE(MoO4)2 (RE = Tb, Dy, Ho, Er, Yb, and Lu)

2020 ◽  
Vol 76 (12) ◽  
pp. 1871-1875
Author(s):  
Saehwa Chong ◽  
Samuel Perry ◽  
Brian J. Riley ◽  
Zayne J. Nelson
Keyword(s):  
Rare Earth ◽  
Crystal Structures ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Using Data ◽  
Cell Volumes ◽  
Rare Earth Molybdates

Six potassium rare-earth molybdates KRE(MoO4)2 (RE = Tb, Dy, Ho, Er, Yb, and Lu) were synthesized by flux-assisted growth in K2Mo3O10. The crystal structures were determined using single-crystal X-ray diffraction data. The synthesized molybdates crystallize with the orthorhombic Pbcn space group (No. 60). Trendlines for unit-cell parameters were calculated using data from the current study. The unit-cell parameters a and c increase linearly whereas b decreases with larger RE cations, based on crystal radii. The unit-cell volumes increase linearly and the densities decrease linearly with larger RE cations. The average distances between the RE cations and the nearest O atoms increase with larger cations whereas the average distances of Mo—O and K—O do not show specific trends.

scholarly journals New crystal structures of adenylate kinase fromStreptococcus pneumoniaeD39 in two conformations

2014 ◽  
Vol 70 (11) ◽  
pp. 1468-1471
Author(s):  
Trung Thanh Thach ◽  
Sangho Lee
Keyword(s):  
Crystal Structures ◽  
Adenylate Kinase ◽  
Bound States ◽  
Critical Role ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Ligand Free ◽  
Adenylate Kinases

Adenylate kinases (AdKs; EC 2.7.3.4) play a critical role in intercellular homeostasis by the interconversion of ATP and AMP to two ADP molecules. Crystal structures of adenylate kinase fromStreptococcus pneumoniaeD39 (SpAdK) have recently been determined using ligand-free and inhibitor-bound crystals belonging to space groupsP21andP1, respectively. Here, new crystal structures of SpAdK in ligand-free and inhibitor-bound states determined at 1.96 and 1.65 Å resolution, respectively, are reported. The new ligand-free crystal belonged to space groupC2, with unit-cell parametersa= 73.5,b= 54.3,c= 62.7 Å, β = 118.8°. The new ligand-free structure revealed an open conformation that differed from the previously determined conformation, with an r.m.s.d on Cαatoms of 1.4 Å. The new crystal of the complex with the two-substrate-mimicking inhibitorP1,P5-bis(adenosine-5′-)pentaphosphate (Ap5A) belonged to space groupP1, with unit-cell parametersa= 53.9,b= 62.3,c= 63.0 Å, α = 101.9, β = 112.6, γ = 89.9°. Despite belonging to the same space group as the previously reported crystal, the new Ap5A-bound crystal contains four molecules in the asymmetric unit, compared with two in the previous crystal, and shows slightly different lattice contacts. These results demonstrate that SpAdK can crystallize promiscuously in different forms and that the open structure is flexible in conformation.

A monotitanate with a stuffed cristobalite structure type

1994 ◽  
Vol 9 (2) ◽  
pp. 146-147 ◽  
Author(s):  
C. Colbeau-Justin ◽  
A. Elfakir ◽  
M. Quarton
Keyword(s):  
Solid State ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Solid State Reaction ◽  
Structure Type ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters

A new titanate K2ZnTiO4 has been synthesized by solid-state reaction. This compound is isostructural with K2ZnGeO4, space group Pca21, Z=8. Unit-cell parameters were determined: a=11.3352(6) Å, b=5.6352(5) Å, c=16.0125(13) Å, and V=1022.8(3) Å3. Powder diffraction data are reported.

Concentration dependences of the unit-cell parameters of nonstoichiometric fluorite-type Na0.5 − x R 0.5 + x F2 + 2x phases (R = rare-earth elements)

2001 ◽  
Vol 46 (2) ◽  
pp. 239-245 ◽  
Author(s):  
P. P. Fedorov ◽  
V. B. Aleksandrov ◽  
O. S. Bondareva ◽  
I. I. Buchinskaya ◽  
M. D. Val'kovskii ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Concentration Dependences ◽  
Fluorite Type

scholarly journals Validation of experimental molecular crystal structures with dispersion-corrected density functional theory calculations

2010 ◽  
Vol 66 (5) ◽  
pp. 544-558 ◽  
Author(s):  
Jacco van de Streek ◽  
Marcus A. Neumann
Keyword(s):  
Density Functional Theory ◽  
Crystal Structures ◽  
Density Functional ◽  
Unit Cell ◽  
Organic Crystal ◽  
Large Temperature ◽  
Unit Cell Parameters ◽  
Functional Theory ◽  
Cell Parameters ◽  
Experimental Crystal

This paper describes the validation of a dispersion-corrected density functional theory (d-DFT) method for the purpose of assessing the correctness of experimental organic crystal structures and enhancing the information content of purely experimental data. 241 experimental organic crystal structures from the August 2008 issue of Acta Cryst. Section E were energy-minimized in full, including unit-cell parameters. The differences between the experimental and the minimized crystal structures were subjected to statistical analysis. The r.m.s. Cartesian displacement excluding H atoms upon energy minimization with flexible unit-cell parameters is selected as a pertinent indicator of the correctness of a crystal structure. All 241 experimental crystal structures are reproduced very well: the average r.m.s. Cartesian displacement for the 241 crystal structures, including 16 disordered structures, is only 0.095 Å (0.084 Å for the 225 ordered structures). R.m.s. Cartesian displacements above 0.25 Å either indicate incorrect experimental crystal structures or reveal interesting structural features such as exceptionally large temperature effects, incorrectly modelled disorder or symmetry breaking H atoms. After validation, the method is applied to nine examples that are known to be ambiguous or subtly incorrect.

The crystal structure of trisodium hexachlororhodate (Na3RhCl6)

2018 ◽  
Vol 33 (1) ◽  
pp. 62-65
Author(s):  
Martin Etter
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Type ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

Commercially available trisodium hexachlororhodate (Na3RhCl6) was dehydrated and characterized by laboratory X-ray powder diffraction. The crystal structure is isostructural to the Na3CrCl6 structure type with space group P$\bar 31$c. Unit-cell parameters are a = 6.8116(1) Å, c = 11.9196(2) Å, V = 478.95(2) Å3, and Z = 2.

Crystal structure and powder data of davidite-type La2Ti10.27Ga9.63O38

1999 ◽  
Vol 14 (1) ◽  
pp. 36-41 ◽  
Author(s):  
A. Meden ◽  
D. Kolar ◽  
S. Škapin
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Structure Type ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters

The structure type of La2Ti10.27Ga9.63O38 was revealed by a search-match using the PDF. A successful Rietveld refinement (Rp=8.9, Rwp=13.3, RB=4.20) confirmed the structure to be rhombohedral (space group R3¯, No. 148) with the refined unit cell parameters a=9.1878(1) Å, α=68.458(1)°, and V=646.374(1) Å3. The structure is compared to other compounds of the davidite type, and the observed and calculated powder data are given.

scholarly journals Crystals of the Arp2/3 complex in two new space groups with structural information about actin-related protein 2 and potential WASP binding sites

2015 ◽  
Vol 71 (9) ◽  
pp. 1161-1168 ◽  
Author(s):  
Christopher T. Jurgenson ◽  
Thomas D. Pollard
Keyword(s):  
Binding Site ◽  
Structural Information ◽  
Unit Cell ◽  
Molecular Structures ◽  
Asymmetric Unit ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Space Groups ◽  
Cell Parameters ◽  
New Space

Co-crystals of the bovine Arp2/3 complex with the CA motif from N-WASP in two new space groups were analyzed by X-ray diffraction. The crystals in the orthorhombic space groupP212121contained one complex per asymmetric unit, with unit-cell parametersa= 105.48,b= 156.71,c= 177.84 Å, and diffracted to 3.9 Å resolution. The crystals in the tetragonal space groupP41contained two complexes per asymmetric unit, with unit-cell parametersa=b= 149.93,c = 265.91 Å, and diffracted to 5.0 Å resolution. The electron-density maps of both new crystal forms had densities for small segments of subdomains 1 and 2 of Arp2. Both maps had density at the binding site on Arp3 for the C-terminal EWE tripeptide from N-WASP and a binding site proposed for the C motif of N-WASP in the barbed-end groove of Arp2. The map from the tetragonal crystal form had density near the barbed end of Arp3 that may correspond to the C helix of N-WASP. The noise levels and the low resolution of the maps made the assignment of specific molecular structures for any of these CA peptides impossible.

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