scholarly journals The crystalline structure of naphthalene. A quantitative X-ray investigation

1933 ◽  
Vol 142 (847) ◽  
pp. 674-688 ◽  
Keyword(s):  
Melting Point ◽  
Single Crystal ◽  
Unit Cell ◽  
Molecular Volume ◽  
Experimental Measurements ◽  
Organic Crystals ◽  
Molecular Symmetry ◽  
Crystal Data ◽  
X Ray ◽  
Small Single Crystal

Crystal Data . Naphthalene .—C 10 H 8 . Melting point 80° C. Density 1·152 (calc. 1·172). Monoclinic prismatic, a = 8·29, b = 5·97, c = 8·68 A., β = 122·7°. Space group C 2λ 5 (P2 1 / a ). Two molecules per unit cell. Molecular symmetry, centre. Molecular volume, 362 A 3 . Total number of electrons per unit cell = F(000) = 136. Experimental—Measurements of Intensities . When a small single crystal is placed completely in an X-ray beam, the integrated reflection is proportional to the mass of the crystal, if the latter is sufficiently small. Although fairly large crystals of naphthalene can easily be obtained, the aim in this work has been to carry out the measurements on specimens small enough for this proportionality to hold good. With soft, organic crystals of the hydrocarbon type, the size required for reliable results is found to be of order of 0·1 milligrams.

scholarly journals Fourier analysis of the durene structure

1933 ◽  
Vol 142 (847) ◽  
pp. 659-674 ◽  
Keyword(s):  
Fourier Analysis ◽  
Unit Cell ◽  
Molecular Volume ◽  
Benzene Derivative ◽  
Molecular Symmetry ◽  
Trial And Error ◽  
Crystal Data ◽  
Precise Information ◽  
X Ray ◽  
Structure Factors

In recent paper the crystal structure of durene, 1. 2. 4. 5. -tetramethyl benzene, has been described. The experimental work, including the measurement of the X-ray intensities, has been dealt with, and the structure deduced to within fairly narrow limits by trial and error methods. In order to obtain more precise information about the orientation and molecular structure of this benzene derivative, a double Fourier analysis has now been applied to the structure factors for the three principal crystallographic zones, and the results are set out below. Crystal Data . Durene .—C 10 H 14 . Melting point 80° C. Density 1⋅03. Monoclinic prismatic. a = 11⋅57, b = 5⋅77, c = 7⋅03 A., β = 113⋅3°. Space group C 2 h 5 (P2 1 / a ). Two molecules per unit cell. Molecular symmetry, centre. Molecular volume, 430 A 3 . Total number of electrons per unit cell = F(000) = 148.

Oxide Structures: By Hook Or by Crook

1998 ◽  
Vol 4 (S2) ◽  
pp. 678-679
Author(s):  
L. D. Marks ◽  
W. Sinkler ◽  
H. Zhang
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Dynamic Range ◽  
Unit Cell ◽  
Crystal Data ◽  
Large Dynamic Range ◽  
Phase Purity ◽  
X Ray ◽  
True Structure

Sometimes oxides are friendly; x-ray or neutron diffraction solves the structure and (at most) simple HREM does a double check. Sometimes they are not. Problems can range from phase purity (identifiable using EDX) to more subtle issues about the true unit cell and/or atom locations. The latter are often particularaly hard for x-ray or neutron to handle when single crystal data is not available and, for instance, the samples are polyphase or textured.One common problem is that the unit cell is rather larger than originally thought due to a superstructure. While superstructure reflections may be obvious in the microscope due to the very large dynamic range of TED patterns, they may not show in powder patterns. The issue then is to determine the true structure using (often) a combination of HREM and TED plus multislice simulations to confirm the structure.

Standard Data for the Identification of Phases By X-Ray Diffraction

1973 ◽  
Vol 17 ◽  
pp. 20-31
Author(s):  
Howard F. McMurdie
Keyword(s):  
Computer Program ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Unit Cell ◽  
National Bureau ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
X Ray ◽  
Standard Data

AbstractThe identification of crystalline phases by x-ray diffraction, either by powder or single crystal techniques requires a dependable body of reference data. It is not only necessary to have data on each phase which are accurate and complete, it also is desirable to have data on as wide a range of compounds as possible, and to have the data organized in such a manner as to be readily usable. The outstanding compilations which approach these goals are the Powder Diffraction File and Crystal Data.The Powder Diffraction File, published by the Joint Committee on Powder Diffraction Standards has data covering about 22,500 phases, both organic and inorganic. These data are of various degrees of accuracy as is indicated by symbols. The File is continuously being improved by the addition of evaluated data from the general literature and by data produced by supporting projects, the principal one being the Joint Committee Associateship at the National Bureau of Standards.To be noted in the File with a star, and to be truly considered standard data a powder pattern must be complete in the sense of including all reflections above the minimum “d” spacing covered, both weak lines and those with large “d” spacings. Since the best test of a pattern is its own internal consistency, the reflections must all have hkl's assigned and must show a good agreement between the spacings observed and those calculated from a refined cell, and they must be consistent with the known space group. This agreement can be best obtained by the use of an internal standard and a computer program. The intensities should be measured by a method which minimizes the effect of crystal orientation.The PDF is provided with search procedure manuals arranged on a scheme of the strongest lines to help in locating data matching that from an unknovm. A computer program for rapid searching is available. A recent development is the inclusion of a “reference intensity” to aid in estimating the quantitative analysis of mixtures.Crystal Data is a compilation now in the third edition made at the National Bureau of Standards and published by the Joint Committee on Powder Diffraction Standards. It contains data on the unit cell parameters of over 24,000 phases. These data are arranged by crystal system and axial ratios to simplify identification of phases from unit cell data obtained from Single crystal cameras.Both of these large compilations are also important reference sources for crystallographic information giving structural information and literature references.

X-Ray Powder Diffraction and Single-Crystal Data for the Isomorphous Series (Fe,Al)3(K,NH4, H3O)H14(PO4)8 ·4H2O

1987 ◽  
Vol 2 (3) ◽  
pp. 187-190 ◽  
Author(s):  
Kjell R. Waerstad ◽  
A. William Frazier
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Crystal Data ◽  
Unit Cell Parameters ◽  
Mixed Salt ◽  
X Ray ◽  
Cell Parameters ◽  
Wet Process ◽  
General Chemical

AbstractX-ray powder diffraction and single-crystal data are reported for a series of isomorphous compounds with the general chemical composition (Fe,Al)3(K,NH4,H3O)H14 (PO4)8·4H2O. The compounds are monoclinic with space group C2/c. Unit-cell parameters were determined on the mixed salt (Fe0.84,Al0.16)3KH14(PO4)8·4H2O, as obtained from sludge precipitated in commercial shipping-grade wet-process phosphoric acid. Single-crystal studies and refined powder diffraction data provided unit-cell parameters of a= 16.908(9) Å, b = 9.588(2) Å, c = 17.539(5) Å, and β = 91.06(4)°.

X-ray powder diffraction analysis of ±-fenoprofen calcium dihydrate

2002 ◽  
Vol 17 (3) ◽  
pp. 244-246
Author(s):  
Ailette Aguila Tobien ◽  
Peter Varlashkin
Keyword(s):  
Single Crystal ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Unit Cell ◽  
Powder Pattern ◽  
Crystal Data ◽  
Racemic Compound ◽  
Internal Standards ◽  
X Ray

The current JCPDS powder pattern for the racemic compound fenoprofen calcium dihydrate (card No. 44-1790) is unindexed. Previously we reported the single crystal data, determined at −100 °C, for this material (Zhu et al., 2001). Using 2θ values obtained from a powder pattern spiked with internal standards, we indexed the room temperature powder pattern. The resulting unit cell values for the monoclinic P21/n cell are a=19.018 Å, b=7.738 Å, c=19.472 Å, β=91.66°.

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 .

Crystal data and X-ray powder diffraction data of 2,4-diiodo-4-nitrophenol (disophenol), C6H3I2NO3. More precise X-ray powder diffraction data of p-nitrophenol, C6H5NO3

1996 ◽  
Vol 11 (4) ◽  
pp. 301-304
Author(s):  
Héctor Novoa de Armas ◽  
Rolando González Hernández ◽  
José Antonio Henao Martínez ◽  
Ramón Poméz Hernández
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Monoclinic Cell

p-nitrophenol, C6H5NO3, and disophenol, C6H3I2NO3, have been investigated by means of X-ray powder diffraction. The unit cell dimensions were determined from diffractometer methods, using monochromatic CuKα1 radiation, and evaluated by indexing programs. The monoclinic cell found for p-nitrophenol was a=6.159(2) Å, b=8.890(2) Å, c=11.770(2) Å, β=103.04(2)°, Z=4, space group P21 or P2l/m, Dx=1.469 Mg/m3. The monoclinic cell found for disophenol has the dimensions a=8.886(1) Å, b=14.088(2) Å, c=8.521(1) Å, β=91.11(1)°, Z=4, space group P2, P2, Pm or P2/m, Dx=2.438 Mg/m3.

scholarly journals Intermetallic REPtZn Compounds with TiNiSi-type Structure

2011 ◽  
Vol 66 (7) ◽  
pp. 671-676 ◽  
Author(s):  
Trinath Mishra ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Coordination Number ◽  
High Frequency ◽  
Three Dimensional ◽  
Type Structure ◽  
Rare Earth Compounds ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray

The equiatomic rare earth compounds REPtZn (RE = Y, Pr, Nd, Gd-Tm) were synthesized from the elements in sealed tantalum tubes by high-frequency melting at 1500 K followed by annealing at 1120 K and quenching. The samples were characterized by powder X-ray diffraction. The structures of four crystals were refined from single-crystal diffractometer data: TiNiSi type, Pnma, a = 707.1(1), b = 430.0(1), c = 812.4(1) pm, wR2 = 0.066, 602 F2, 21 variables for PrPt1.056Zn0.944; a = 695.2(1), b = 419.9(1), c = 804.8(1) pm, wR2 = 0.041, 522 F2, 21 variables for GdPt0.941Zn1.059; a = 688.2(1), b = 408.1(1), c = 812.5(1) pm, wR2 = 0.041, 497 F2, 22 variables for HoPt1.055Zn0.945; a = 686.9(1), b = 407.8(1), c = 810.4(1) pm, wR2 = 0.061, 779 F2, 20 variables for ErPtZn. The single-crystal data indicate small homogeneity ranges REPt1±xZn1±x. The platinum and zinc atoms build up three-dimensional [PtZn] networks (265 - 269 pm Pt-Zn in ErPtZn) in which the erbium atoms fill cages with coordination number 16 (6 Pt + 6 Zn + 4 Er). Bonding of the erbium atoms to the [PtZn] network proceeds via shorter RE-Pt distances, i. e. 288 - 293 pm in ErPtZn.

Lewis-Base Adducts of Group 1B Metal(I) Compounds. XXI The Crystal and Molecular Structures of the Unsolvated Forms of Dibromotris(triphenylphosphine)dicopper(I) and 'step' Tetrabromotetrakis(triphenyl-phosphine)tetracopper(I)

1985 ◽  
Vol 38 (8) ◽  
pp. 1243 ◽  
Author(s):  
JC Dyason ◽  
LM Engelhardt ◽  
C Pakawatchai ◽  
PC Healy ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Molecular Structures ◽  
Lewis Base ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Triphenyl Phosphine ◽  
X Ray ◽  
Crystal And Molecular Structures

The crystal structures of the title compounds have been determined by single-crystal X-ray diffraction methods at 295 K. Crystal data for (PPh3)2CuBr2Cu(PPh3) (1) show that the crystals are iso-morphous with the previously studied chloro analogue, being monoclinic, P21/c, a 19.390(8), b 9.912(5), c 26.979(9) Ǻ, β 112,33(3)°; R 0.043 for No 3444. Cu( trigonal )- P;Br respectively are 2.191(3); 2.409(2), 2.364(2) Ǻ. Cu(tetrahedral)- P;Br respectively are 2.241(3), 2.249(3); 2.550(2), 2.571(2) Ǻ. Crystals of 'step' [PPh3CuBr]4 (2) are isomorphous with the solvated bromo and unsolvated iodo analogues, being monoclinic, C2/c, a 25.687(10), b 16.084(7), c 17.815(9) Ǻ, β 110.92(3)°; R 0.072 for No 3055. Cu( trigonal )- P;Br respectively are 2.206(5); 2.371(3), 2.427(2) Ǻ. Cu(tetrahedral)- P;Br are 2.207(4); 2.446(2), 2.676(3), 2.515(3) Ǻ.

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