CRYSTAL CHEMISTRY OF MERCURY SULFOHALIDES OF COMPOSITION Hg3S2Hal2 (Hal: Cl, Br). II. CRYSTAL STRUCTURES OF TWO POLYMORPHIC MODIFICATIONS OF Hg3S2Br2-xClx (x   0.5)

2006 ◽  
Vol 44 (5) ◽  
pp. 1247-1255 ◽  
Author(s):  
N. V. Pervukhina ◽  
V. I. Vasil'ev ◽  
S. A. Magarill ◽  
S. V. Borisov ◽  
D. Yu. Naumov
Keyword(s):  
Crystal Structures ◽  
Crystal Chemistry ◽  
Polymorphic Modifications

scholarly journals Nets with collisions (unstable nets) and crystal chemistry

2013 ◽  
Vol 69 (6) ◽  
pp. 535-542 ◽  
Author(s):  
Olaf Delgado-Friedrichs ◽  
Stephen T. Hyde ◽  
Shin-Won Mun ◽  
Michael O'Keeffe ◽  
Davide M. Proserpio
Keyword(s):  
Crystal Structures ◽  
Crystal Chemistry ◽  
Barycentric Coordinates ◽  
Real Crystal ◽  
Crystallographic Symmetry

Nets in which different vertices have identical barycentric coordinates (i.e.have collisions) are called unstable. Some such nets have automorphisms that do not correspond to crystallographic symmetries and are called non-crystallographic. Examples are given of nets taken from real crystal structures which have embeddings with crystallographic symmetry in which colliding nodes either are, or are not, topological neighbors (linked) and in which some links coincide. An example is also given of a crystallographic net of exceptional girth (16), which has collisions in barycentric coordinates but which also has embeddings without collisions with the same symmetry. In this last case the collisions are termedunforced.

Crystal structures and electronic properties of Sn3N4 polymorphs synthesized via high-pressure nitridation of tin

CrystEngComm ◽  
2020 ◽  
Vol 22 (20) ◽  
pp. 3531-3538
Author(s):  
Ken Niwa ◽  
Tomoya Inagaki ◽  
Tetsu Ohsuna ◽  
Zheng Liu ◽  
Takuya Sasaki ◽  
...  
Keyword(s):  
High Pressure ◽  
Electronic Properties ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Diamond Anvil Cell ◽  
Functional Materials ◽  
Group Iva ◽  
Diamond Anvil ◽  
Laser Heated ◽  
Insight Into

Sn3N4 polymorphs were synthesized via high-pressure nitridation of tin by means of laser-heated diamond anvil cell technique. This implies new insight into the crystal chemistry and functional materials of group IVA nitrides.

Two polymorphs of 2-ethyl-3-hydroxy-6-methylpyridinium hydrogenN-acetyl-L-glutamate from powder diffraction data

2013 ◽  
Vol 69 (12) ◽  
pp. 1549-1552 ◽  
Author(s):  
Vladimir V. Chernyshev ◽  
Sergey Y. Efimov ◽  
Ksenia A. Paseshnichenko ◽  
Andrey A. Shiryaev
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Crystal Packing ◽  
Three Dimensional ◽  
Powder Diffraction Data ◽  
Screw Axis ◽  
Dimensional Network ◽  
Polymorphic Modifications

The title salt, C8H12NO+·C7H10NO5−, crystallizes in two polymorphic modifications,viz.monoclinic (M) and orthorhombic (O). The crystal structures of both polymorphic modifications have been established from laboratory powder diffraction data. The crystal packing motifs in the two polymorphs are different, but the conformations of the anions are generally similar. InM, the anions are linked by pairs of hydrogen bonds of the N—H...O and O—H...O types into chains along theb-axis direction, and neighbouring molecules within the chain are related by the 21screw axis. The cations link these chainsviaO—H...O and N—H...O hydrogen bonds into layers parallel to (001). InO, the anions are linked by O—H...O hydrogen bonds into helices along [001], and neighbouring molecules within the helix are related by the 21screw axis. The neighbouring helical turns are linked by N—H...O hydrogen bonds. The cations link the helicesviaO—H...O and N—H...O hydrogen bonds, thus forming a three-dimensional network.

Influence of ortho-substituent on the molecular and crystal structures of 2-(N-arylimino)coumarin-3-carboxamide: isotypic and polymorphic structures

2019 ◽  
Vol 75 (5) ◽  
pp. 887-902 ◽  
Author(s):  
Svitlana V. Shishkina ◽  
Irina S. Konovalova ◽  
Sergiy M. Kovalenko ◽  
Pavlo V. Trostianko ◽  
Anna O. Geleverya ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Polymorphic Modification ◽  
Aryl Group ◽  
Group Iii ◽  
Pairwise Interactions ◽  
Group I ◽  
Polymorphic Modifications ◽  
Molecular And Crystal Structures

During a comprehensive study of a series of 2-(N-arylimino)coumarin-3-carboxamides with the aryl group substituted in the ortho-position by either a halogen atom, a methyl group or a methoxy group, the existence of three groups of isotypic crystal structures has been revealed. The similarity of crystal structures belonging to the same groups was confirmed by the analysis based on the comparison of pairwise interactions energies obtained from quantum chemical calculations. Group I includes unsubstituted, methyl-substituted and polymorphic modification 1 of fluoro-substituted 2-(N-arylimino)coumarin-3-carboxamide. Structures of polymorphic modification 2 of fluoro-substituted derivative, chloro-substituted and polymorphic modification 1 of bromo-substituted 2-(N-arylimino)coumarin-3-carboxamide may represent group II. Group III contains structures of polymorphic modification 2 of bromo-substituted derivative, iodine- and methoxy-substituted 2-(N-arylimino)coumarin-3-carboxamides. Structures of the same type group have extremely close parameters of the unit cell as well as those of molecular and crystal structures. But they are not identical. Polymorphic modifications of fluoro- and bromo-substituted 2-(N-arylimino)coumarin-3-carboxamides belong to different crystal types mainly due to different arrangement of basic structural motifs separated out using quantum chemical calculations.

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