scholarly journals VI. Tabulated data for the examination of the 230 space-groups by homogeneous X-rays

1924 ◽  
Vol 224 (616-625) ◽  
pp. 221-257 ◽  
Keyword(s):  
Crystal Structures ◽  
Chemical Society ◽  
Unit Cell ◽  
X Rays ◽  
Screw Axis ◽  
Monoclinic System ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Relative Arrangement

The object of the present paper is to express the conclusions of mathematical crystallography in a form which shall be immediately useful to workers using homogeneous X-rays for the analysis of crystal structures. The results are directly applicable to such methods as the Bragg ionisation method, the powder method, the rotating crystal method, etc., and summarise in as compact a form as possible what inferences may be made from the experimental observations, whichever one of the 230 possible space-groups may happen to be under examination. It is only in certain cases that the spacings of crystal planes as determined by the aid of homogeneous X-rays agree with the values of those spacings which would be expected from ordinary crystallographic calculations. In the majority of cases the relative arrangement of the molecules in the unit cell leads to apparent anomalies in the experimental results, the observed spacings of certain planes or sets of planes being sub-multiples of the calculated spacings. The simplest case (fig. 8) of such an apparent anomaly is found in the space-group C 2 2 of the monoclinic system, where the presence of a two-fold screw-axis, because it interleaves halfway the (010) planes by molecules which are exactly like those lying in the (010) planes, except that they have been rotated through 180°, leads to an observed periodicity which is half the periodicity to be inferred from the dimensions of the unit cell, that is, leads to an observed spacing for (010) which is half the calculated. All screw-axes produce similar results, and, in general, a p -fold screw-axis leads to an observed spacing for the plane perpendicular to it which is 1/ p th that to be inferred from the dimensions of the cell. Besides those produced by the screw-axes, other abnormalities arise out of the presence of glide-planes. The simplest case of this is shown by the space-group C s 2 (fig. 4) of the monoclinic system, in which the second molecule is obtained from the first by a reflection in a plane parallel to (010) and half a primitive translation parallel to that plane. If we look along a direction perpendicular to this glide-plane, the projections of the two molecules on the (010) plane are indistinguishable except in position, which is equivalent to saying that, for the purposes of X-ray interference, certain planes perpendicular to this plane of projection are interleaved by an identical molecular distribution. Furthermore, since the translation associated with the glide-plane must always be half a primitive translation parallel to the glide-plane, we know that the interleaving is always a submultiple of the full spacing and the periodicity is again reduced in a corresponding manner. The use of this method for discriminating between the various space-groups of the monoclinic system was described by Sir Wm. Bragg in a lecture to the Chemical Society. In the present paper the method has been extended to the whole of the 230 space-groups possible to crystalline structures. In general, it may be said that if a crystal possesses a certain glide-plane, a certain set of planes lying in the zone whose axis is perpendicular to that glide-plane will have their periodicity reduced by one-half.

Molecular and Crystal Structure of Sildenafil Base

2012 ◽  
Vol 67 (5) ◽  
pp. 491-494 ◽  
Author(s):  
Dmitrijs Stepanovs ◽  
Anatoly Mishnev
Keyword(s):  
Crystal Structure ◽  
Erectile Dysfunction ◽  
Crystal Structures ◽  
Unit Cell ◽  
Sildenafil Citrate ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

Sildenafil citrate monohydrate, well known as Viagra®, is a drug for the treatment of erectile dysfunction. Here we present the X-ray crystal structure of the sildenafil base, C22H30N6O4S. The compound crystallizes in the monoclinic system, space group P21/c with the unit cell parameters a = 17:273(1), b=17:0710(8), c=8:3171(4) Å , b =99:326(2), Z = 4, V = 2420:0(3) Å3. A comparison with the known crystal structures of sildenafil citrate monohydrate and sildenafil saccharinate is also presented.

scholarly journals Symmetry Relations Between Space Groups in Layered Germanate Structures: Modeling Crystal Structures

2014 ◽  
Vol 70 (a1) ◽  
pp. C1763-C1763
Author(s):  
Nelly Flores-Sanchez ◽  
Ivonne Rosales ◽  
Lauro Bucio
Keyword(s):  
Crystal Structures ◽  
Rietveld Refinement ◽  
Structural Model ◽  
Structural Data ◽  
X Rays ◽  
Monoclinic System ◽  
Space Group ◽  
Space Groups ◽  
Group Type ◽  
Symmetry Relations

Structural models for the new layered germanates ScInGe2O7 and ScFeGe2O7 were analyzed within the framework of symmetry relations between space groups. These compounds were supposed to be hettotypes of the thortveitite mineral, (Sc,Y)2Si2O7, which was considered as the aristotype. Thortveitite crystallizes in the monoclinic system, and the symmetry is described by the space group type C2/m. Other monoclinic hettotypes for the thortveitite are FeInGe2O7 (PDF 01-070-8447, ICSD - 94487), space group C2/m (No. 12); TbInGe2O7 (PDF 01-072-6515, ICSD - 96360), space group C2/c (No. 15); and FeYGe2O7 (PDF 01-072-6099, ICSD - 95935), space group P21/m (No. 11). All these space groups are related by symmetry. By the use of these relations, we proposed starting models for the crystal structures of ScInGe2O7 and ScFeGe2O7. For ScInGe2O7 this was found to be isostructural to FeInGe2O7 reported by our laboratory [1]. The structural data for this compound were obtained by conventional Rietveld refinement of the powder diffraction data of X-rays, using the GSAS program and EXPGUI [2, 3] interface. For ScFeGe2O7 the symmetry related structural model was found in the triclinic system by symmetry reduction from the space group C2/m (unique axis b) to the triclinic space group P1 (figure 1). Rietveld refinement was performed reaching to the following results: lattice parameters a = 5.3434 (8), b = 5.3145 (8), c = 4.8732 (7 ) Å, α = 99 468 (2), β = 97 257 (2), γ = 104 609 (2)0, V = 130.03 (5) A3, Z = 1; WRp = 0.047, Rp = 0.04 and reduced χ2 of 2.176 for 64 variables. This study was sponsored by CONACyT project CB-2011/167624.

scholarly journals An X-ray analysis of the structure of chrysene

1934 ◽  
Vol 146 (856) ◽  
pp. 140-153 ◽  
Keyword(s):  
Room Temperature ◽  
Unit Cell ◽  
Molecular Volume ◽  
Crystal Data ◽  
Monoclinic System ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Measured Density

Chrysene crystallizes in the monoclinic system. By means of rotation, oscillation, and moving film photographs the following crystal data have been obtained:— a = 8·34 A, b = 6·18 A, c = 25·0 A, β = 115·8°. All the planes ( hkl ) are halved when h + k + l is odd and in addition all the ( h 0 l ) planes are halved. There are two space groups available, C 6 2 h (I2/ c ) and C 4 s (I c ). In what follows it will be shown that the former space group is the more probable. The measured density is 1·27 (at room temperature) giving 4 molecules of C 18 H 12 per unit cell. Molecular volume = 290 (A) 3 .

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.

An explanation for the origin of hemihedrism in wulfenite: the single-crystal structures of I4̄1/a and I4̄ tungstenian wulfenites

2000 ◽  
Vol 64 (6) ◽  
pp. 1057-1062 ◽  
Author(s):  
D. E. Hibbs ◽  
C. M. Jury ◽  
P. Leverett ◽  
I. R. Plimer ◽  
P. A. Williams
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
San Francisco ◽  
Analytical Data ◽  
Site Occupancy ◽  
Unit Cell ◽  
Special Position ◽  
Space Group ◽  
X Ray ◽  
Single Crystal Structures

AbstractThe single-crystal X-ray structure of tungstenian wulfenite-I41/a containing 10 mol.% WO3 from the San Francisco mine, Sonora, Mexico, space group I41/a, a = 5.436(2), c = 12.068(8)Å and Z = 4, has been refined to R = 0.052. The Mo and W are disordered over special position 4a (0,0,0) in the lattice. Tungstenian wulfenite-I4̄ (‘chillagite’) from the Christmas Gift mine, Chillagoe, Queensland, Australia (Museum of Victoria specimen M16934), crystallizes in the closely related tetragonal space group I4̄, with a = 5.441(1), c = 12.068(6) Å and Z = 4. The structure was refined to R = 0.038. Refined site occupancy factors show that Mo and W are not distributed equally over the two crystallographically independent Mo/W positions, being 0.136(2) for Mo and 0.114(2) for W in special position 2a (0,0,0) and 0.184(2) for Mo and 0.066(2) for W in special position 2c (0,Ý,Ü). These give a composition corresponding to wulfenite64stolzite36, in agreement with analytical data. The Mo/W distributions in the unit cell provide one explanation for the origin of hemihedrism in the wulfenite-stolzite series.

Synthesis and X-ray diffraction data of 1-N-(4-pyridylmethyl)amino naphthalene

2010 ◽  
Vol 25 (1) ◽  
pp. 72-74 ◽  
Author(s):  
H. A. Camargo ◽  
J. A. Henao ◽  
D. F. Amado ◽  
V. V. Kouznetsov
Keyword(s):  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

1-N-(4-pyridylmethyl)amino naphtalene was synthesized by means of a reaction of alpha-naphthylamine, 4-pyridylcarboxyaldehyde, in anhydrous ethanol to obtainN-(4-pyridylen)-alpha-naphthylamine and that was reduced with NaBH4 to produce the wanted compound. The X-ray powder diffraction pattern for the new compound 1-N-(4-pyrydylmethyl)amino naphtalene was obtained. This compound crystallizes in a monoclinic system with refined unit cell parameters a=10.375(5) Å, b=17.665(6) Å, c=5.566(2) Å, β=100.11(3), and V=1004.3(5) Å3, with space group P2/m (No. 10).

X-Ray Investigations on Some Salts of Hydrazine and Hydrazine Derivatives

1961 ◽  
Vol 5 ◽  
pp. 133-141 ◽  
Author(s):  
M. Stammler ◽  
D. Orcutt
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
X Ray ◽  
Space Groups ◽  
Inorganic Acids ◽  
Cell Dimensions ◽  
System Cell ◽  
Diffraction Patterns ◽  
Perchlorate Salt

AbstractThe salts of hydrazine or methyl derivatives of hydrazine were prepared by neutralization of the base with inorganic acids, for instance, HBF4, HClO4, H SO4, and HCl. Upon recrystallization of the product from a suitable solvent, X-ray diffraction patterns were obtained. Hydrazine tetrafluoborate H2N-NH2·HBF4 was found to crystallize in the monoclinic system. Cell dimensions and possible space groups were determined. The corresponding perchlorate salt crystallizes in two forms, one of which is isomorphous with hydrazine tetrafluoborate. The second form seems to be stabilized by small amounts of water.The tetrafluoborate salt was prepared from the 1,1-dimethyl hydrazine. It was found to crystallize in the tetragonal system with a primitive unit cell. The perchlorate salt of this base is isomorphous with the fluoborate but with a slightly larger unit cell. Both materials undergo plastic-like deformation. The general appearance and mechanical properties are similar to those of a hydrocarbon wax. The 1,1-dimethyl hydrazine sulfate and the 1,1-dimethyl hydrazine hydrochloride have a lower symmetry than the HBF4 salt and do not show the wax-like properties of the latter. Based on the study of these chemically related compounds an explanation is offered for the properties of 1,1-dimethyl hydrazine tetrafluoborate in terms of crystalline structure.

scholarly journals Crystal Structures of Two Macrocyclic Bischalcones Possessing 26-Membered Rings

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Rina Mondal ◽  
Nayim Sepay ◽  
Debajyoti Ghoshal ◽  
Asok K. Mallik
Keyword(s):  
Hydrogen Bonding ◽  
Single Crystal ◽  
Crystal Structures ◽  
Membered Ring ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Hydrogen Bonding Interactions

Single crystal X-ray diffraction of two macrocyclic bischalcones, namely, (2E,25E)-11,17,33,37-tetraoxapentacyclo[36.4.0.05,10.018,23.027,32]dotetraconta-1(42),2,5,7,9,18,20,22,25,27,29,31,38,40-tetradecaene-4,24-dione(1) and (2E,24E)-11,16,32,37-tetraoxapentacyclo[36.4.0.05,10.017,22.026,31]dotetraconta-1(42),2,5,7,9,17,19,21,24,26,28,30,38,40-tetradecaene-4,23-dione(2), each containing a 26-membered ring, has been studied. Compound 1 belongs to the monoclinic system, space group C2/c with a = 34.3615(9) Å, b = 12.7995(3) Å, c = 14.6231(3) Å, β = 96.912(2)°,  V = 6,384.6(3) Å3, and Z = 8. Compound 2 is triclinic, space group P-1 with a = 10.066(2) Å, b = 10.670(3) Å, c = 16.590(3) Å, α = 85.95(2), β = 89.244(14), γ = 62.211(13), V = 1572.0(6) Å3, and Z = 2. Intermolecular C–H⋯O hydrogen bonding interactions are present in both compounds.

The crystal structures of Cu1•8Se, Cu3Se2, α- and γCuSe, CuSe2, and CuSe2II

1976 ◽  
Vol 54 (6) ◽  
pp. 841-848 ◽  
Author(s):  
Robert Donald Heyding ◽  
Ritchie MacLaren Murray
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Unit Cell ◽  
Intensity Data ◽  
Diffraction Intensity ◽  
Space Group ◽  
X Ray ◽  
Model Based ◽  
Tetrahedral Sites

The crystal structures of a number of copper selenides have been re-examined using X-ray powder diffraction intensity data. |F0| values for Cu1•8Se at room temperature (a = 5.765 Å) are satisfied by a model based on space group Fm3m with 4 Se atoms per unit cell on the fcc sites, 5.2 Cu atoms on the tetrahedral sites, and 2.0 Cu atoms on the trigonal sites in the Se sublattice. Cu3Se2 is tetragonal, [Formula: see text] a = 6.402, c = 4.279 Å, with Cu(1) in 2(a), Cu(2) in 4(e) with x = 0.147 ± 5, z = 0.781 ± 9, and Se in 4(e) with x = 0.272 ± 3, z = 0.264 ± 7. CuSe2 has the orthorhombic C18 marcasite structure, Pnnm, a = 5.005, b = 6.182, c = 3.740 Å, with Cu in 2(a), and Se in 4(g) with x = 0.184 ± 1, y = 0.385 ± 1. CuSe2II has the cubic C2 pyrite structure, Pa3, a = 6.116 Å, with Cu in 4(a), and Se in 8(c) with x = 0.3891 ± 5.Neither αCuSe nor γCuSe have the CuS covellite structure.These results are discussed in some detail.

Diagrammes de poudres de l'iminostilbene, C14H11N, de l'iminodibenzyle, C14H13N, et de son derivé: le chloro-3 iminodibenzyle, C14H12ClN

1983 ◽  
Vol 16 (6) ◽  
pp. 649-649
Author(s):  
C. Caranoni ◽  
J. P. Reboul
Keyword(s):  
Crystal Structures ◽  
Psychotropic Drugs ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Orthorhombic Unit Cell ◽  
Acta Cryst ◽  
Space Group ◽  
X Ray ◽  
Lattice Constants

X-ray powder data have been obtained for the three title compounds, fundamental members of a group of psychotropic drugs. For the first two compounds, the crystal structures of which have previously been solved [Reboul, Cristau, Soyfer & Estienne (1980). Acta Cryst. B36, 2683–2688; Reboul, Cristau, Estienne & Astier, (1980). Acta Cryst. B36, 2108–2112], the powder patterns were indexed on the basis of an orthorhombic unit cell with the lattice constants a = 8.22 (1), b = 20.40 (1), c = 6.03 (1) Å, space group Pnma for C14H11N; C14H13N is monoclinic, space group P21/c with a = 11.60 (1), b = 11.27 (1), c = 20.05 (1) Å, and β = 126.5 (1)°. C14H12ClN is also monoclinic, P21 or P21/m, with Z = 2, a = 11.68 (1), b = 8.08 (1), c = 12.13 (1) Å and β = 95.6 (1)°. The JCPDS Diffraction File Nos. for these compounds are: C14H11N 34-1995; C14H13N 34-1996, C14H12ClN 34-1994.

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