Some Effects of Crystal Structure on Production of Radicals in Irradiated Organic Crystals

1968 ◽  
pp. 327-335 ◽  
Author(s):  
MAX T. ROGERS ◽  
L. D. KISPERT
Keyword(s):  
Crystal Structure ◽  
Organic Crystals

scholarly journals Insight from energy surfaces: structure prediction by lattice energy exploration

2014 ◽  
Vol 70 (a1) ◽  
pp. C28-C28
Author(s):  
Graeme Day
Keyword(s):  
Crystal Structure ◽  
Structure Prediction ◽  
Crystal Packing ◽  
Lattice Energy ◽  
Organic Crystals ◽  
Crystal Structure Prediction ◽  
Stability Order ◽  
The Stability ◽  
Solid Form ◽  
Energy Surfaces

A long-standing challenge for the application of computational chemistry in the field of crystallography is the prediction of crystal packing, given no more than the chemical bonding of the molecules being crystallised. Recent years have seen significant progress towards reliable crystal structure prediction methods, even for traditionally challenging systems involving flexible molecules and multi-component solids [1]. These methods are based on global searches of the lattice energy surface: a search is performed to locate all possible packing arrangements, and these structures are ranked by their calculated energy [2]. One aim of this lecture is to provide an overview of advances in methods for crystal structure prediction, focussing on molecular organic crystals, and highlighting strategies that are being explored to extend the reach of these methods to more complex systems. A second aim is to discuss the range applications of crystal structure prediction calculations, which have traditionally included solid form screening, particularly of pharmaceutically active molecules, and structure determination. As energy models become more reliable at correctly ranking the stability order of putative structures, and the timescale required for structure searching decreases, crystal structure prediction has the potential for the discovery of novel molecular materials with targeted properties. Prospects for computer-guided discovery of materials will be discussed.

scholarly journals The structure of resorcinol a quantitative X-ray investigation

1936 ◽  
Vol 157 (890) ◽  
pp. 79-99 ◽  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Solid State ◽  
Hydroxyl Group ◽  
Organic Crystals ◽  
Physical Explanation ◽  
Aromatic Carbon ◽  
X Ray ◽  
Reactive Groups ◽  
Intermolecular Distances

Previous investigations of organic crystals have served to determine the dimensions and structure of the aromatic carbon ring and of certain simple substituent groups. The hydroxyl group is particularly interesting, both in relation to chemistry and in the physical explanation of its associating properties. A considerable number of metallic hydroxides has been studied by X-ray analysis, and the results show that the occurrence of the —OH group is generally characterized in the solid state by unusually small intermolecular distances. It is obviously of the greatest importance to study the dimensional properties of these groups in organic acids, phenols, and alcohols, but until now few really quantitative investigations along these lines have been carried out. The properties of the phenols, intermediate as they are between those of the acids and the alcohols, would lead us to expect the characteristic hydroxyl or hydrogen bond distances (2·5 to 2·8 A) between the reactive groups on adjoining molecules; but the question arises whether this can be achieved in the crystal structure without sacrificing the usual minimum van der Waals distance of about 3·5 A, between some of the aromatic carbon atoms of the molecules. The solution of the present structure shows that these two distinct sets of intermolecular distances are, in fact, retained without bringing in any intermediate values.

scholarly journals The crystal structure of pentaerythritol tetracetate.

1938 ◽  
Vol 164 (918) ◽  
pp. 369-383 ◽  
Author(s):  
T. H. Goodwin ◽  
R. Hardy ◽  
William Lawrence Bragg
Keyword(s):  
Crystal Structure ◽  
Carbon Atom ◽  
Fourier Analysis ◽  
Reliable Information ◽  
Organic Crystals ◽  
X Rays ◽  
Central Carbon Atom ◽  
Central Carbon

Although the technique for investigating organic crystals by X-rays is now fairly well developed, there are still many important types of compound of which no representative has yet been examined. In particular no Fourier analysis of an ester has ever been published and no reliable information is available as to the lengths of C—O and C=O bonds in such substances. The investigation of pentaerythritol tetracetate recorded here was made partly to supply this deficiency and partly to develop the study of pentaerythritol (Llewellyn, Cox and Goodwin 1937). A further incentive lay in the doubt which existed at one time regarding the distribution of the valencies of the central carbon atom in the tetracetate; this is discussed in § III. The results of the investigation are presented at once, the methods by which they were deduced being described in the last section.

Solvent effects on morphology and crystal structure of solution-grown organic crystals

2001 ◽  
Author(s):  
Bernard Marciniak ◽  
Ewa Rozycka-Sokolowska ◽  
W. Pawliuk
Keyword(s):  
Crystal Structure ◽  
Solvent Effects ◽  
Organic Crystals

Effect of accelerating voltage on electron diffraction structure analysis of organic crystals: Copper perchlorophthalocyanine

1991 ◽  
Vol 49 ◽  
pp. 794-795
Author(s):  
D. L. Dorset ◽  
W. F. Tivol ◽  
J. N. Turner
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Crystal Thickness ◽  
Organic Crystals ◽  
Intensity Data ◽  
Optimal Conditions ◽  
High Angle ◽  
Ewald Sphere ◽  
Diffraction Structure ◽  
Optimal Wavelength

It is well known that the perturbation of measured electron diffraction intensities from thin microcrystals by multiple beam dynamical scattering is a function of crystal thickness, atomic number of the crystal components and the electron wavelength. For organic crystals, an attempt was made to calculate optimal conditions for collecting intensity data in order to permit ab intio crystal structure analyses to be carried out. Although the maximum crystal thickness giving quasi-kinematical diffraction intensities was found to increase with electron accelerating voltage, as expected, an optimal wavelength was also determined, beyond which the flattening of the Ewald sphere was expected to bring more high angle reflections into the convolution terms of the multi-slice expression. However, this latter aspect may actually be incorrectly represented by the computational model, because the significant thermal motion found for many organic crystals was not considered. For this reason, an experimental evaluation of the problem is being made using thin epitaxial crystals of copper perchlorophthalocyanine.

scholarly journals An X-ray investigation of the structure of naphthalene and anthracene

1929 ◽  
Vol 125 (798) ◽  
pp. 542-569 ◽  
Keyword(s):  
Crystal Structure ◽  
Geometrical Structure ◽  
Organic Crystals ◽  
X Rays ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Scattering Centre ◽  
Low Symmetry ◽  
Complicated Nature ◽  
Long Chain

In the present paper an attempt is made to develop a geometrical structure factor which will account for the intensity distribution in the various spectra of naphthalene and anthracene. Such an attempt is surrounded by many difficulties owing to the relatively low symmetry of the crystal systems (monclinic), the complicated nature of the molecules, and uncertainties regarding the laws of reflection of X-rays from organic crystals. Recently, however, Dr. Müller has investigated the structure of a long chain hydrocarbon making the simplication of treating a carbon atom and its attendent hydrogen atoms as one scattering centre for X-rays. The success of this investigation makes it seem probable that an approximate structure may likewise be obtained for some of the more complicated aromatic compounds. The simple organic compounds of this type (benzene, cyclohexane) are very often liquids or low melting solids that call for a specialised and difficlut technique in any investigation of their crystal structure. Good crystals of naphthalene and anthracene, however, are easily obtained. Morever the crystal structure of these compounds has already been investigated very fully by Sir William Bragg, both by the ionisation spectrometer and photographic methods. The author has had the privilege of assisting in some of this later work, and the present paper is a continuation of these investigations.

Sizes of molecules in organic crystals: the Voronoi–Dirichlet approach

2004 ◽  
Vol 60 (4) ◽  
pp. 447-452 ◽  
Author(s):  
Igor A. Baburin ◽  
Vladislav A. Blatov
Keyword(s):  
Crystal Structure ◽  
Good Deal ◽  
Organic Crystals ◽  
Molecular Sizes

The sizes of more than 100 000 molecules in organic crystals have been assessed as the volumes of molecular Voronoi–Dirichlet polyhedra. The average molecular volumes for all crystals are shown to be nearly equal to the corresponding values in homomolecular (consisting of identical molecules) crystals. The validity of the Voronoi–Dirichlet approach in determining molecular sizes is substantiated and the reasons for the variations in the molecular volumes are discussed. It is shown that a molecule increases its volume if it is surrounded by a good deal of high-row (i.e. an element with more than ten protons) atoms or if there is disorder in the crystal structure.

scholarly journals Understanding stress-induced disorder and breakage in organic crystals: beyond crystal structure anisotropy

2021 ◽  
Author(s):  
Gabriela Schneider-Rauber ◽  
Mihails Arhangelskis ◽  
Wei-Pin Goh ◽  
James Cattle ◽  
Nicole Hondow ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Engineering ◽  
Organic Crystals ◽  
Organic Solids ◽  
Design And Synthesis

Crystal engineering has advanced the strategies of design and synthesis of organic solids with the main focus being on customising the properties of the materials.

Sign in / Sign up

Export Citation Format

Share Document