scholarly journals The crystal structure of high temperature form of kalsilite (KAlSiO4) at 950.DEG.C.

1987 ◽  
Vol 13 (5) ◽  
pp. 260-270 ◽  
Author(s):  
A. KAWAHARA ◽  
Y. ANDOU ◽  
F. MARUMO ◽  
M. OKUNO
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Temperature Form ◽  
High Temperature Form

scholarly journals Comparison of the crystal structures of the low- and high-temperature forms of bis[4-(dimethylamino)pyridine]dithiocyanatocobalt(II)

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Christoph Krebs ◽  
Inke Jess ◽  
Christian Näther
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Three Dimensional ◽  
Monoclinic Space Group ◽  
Temperature Form ◽  
Dimensional Network ◽  
High Temperature Form

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-dimethylaminopyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thiocyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C—H...S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C—H...S and C—H...N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.457 g cm−3) is lower than that of the low-temperature form II (ρ = 1.462 g cm−3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive intermolecular hydrogen bonding in form II might be responsible.

The incommensurately modulated crystal structure of β-Pb2BiVO6: interpretation of the phase transition α → β → δ and conduction properties of related materials

2009 ◽  
Vol 65 (4) ◽  
pp. 416-425 ◽  
Author(s):  
Pascal Roussel ◽  
Olfa Labidi ◽  
Marielle Huve ◽  
Michel Drache ◽  
Jean-Pierre Wignacourt ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Structural Investigations ◽  
Modulated Structure ◽  
Temperature Form ◽  
Incommensurate Modulation ◽  
High Temperature Form ◽  
Conduction Properties

A new polymorph of Pb2BiVO6 was prepared under ambient conditions and its crystal structure was determined by single-crystal X-ray diffraction. The phase transitions α → β and β → δ were identified in the mother phase; the high-temperature form δ-Pb2BiVO6 eventually decomposes at 753 K to a mixture of Pb4BiVO8 and the high-temperature form of PbBiVO5 before showing recombination at 923 K. β-Pb2BiVO6 has an incommensurate monoclinic modulated structure. This crystal structure is twinned and complementary structural investigations of a powder sample of β-Pb2BiVO6 by TEM diffraction studies confirmed the lattice and incommensurate modulation character. Log σ = f(T −1) dependences for Pb2BiVO6-related materials (6% M-for-V-substituted compositions; M = Cr, Mn, P) are reported, which allow the characterization (E a and isothermal σ values) of the β- as well as the δ- and α-Pb2BiVO6 varieties.

scholarly journals On the Crystal Structure of the High-temperature Form of Silver Nitrate (AgNO3-I).

1970 ◽  
Vol 24 ◽  
pp. 1477-1479 ◽  
Author(s):  
K. O. Strømme ◽  
Jean Galy ◽  
Karl-Axel Wilhelmi ◽  
A. Nørlund Christensen ◽  
S. E. Rasmussen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Silver Nitrate ◽  
Temperature Form ◽  
High Temperature Form

X-ray investigation of bredigite

1952 ◽  
Vol 29 (217) ◽  
pp. 875-884 ◽  
Author(s):  
Audrey M. B. Douglas
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Single Crystal ◽  
Hexagonal Phase ◽  
Natural Mineral ◽  
X Ray ◽  
Temperature Form ◽  
County Antrim ◽  
High Temperature Form ◽  
Different Sources

The X-ray work described below has been done on crystals of bredigite obtained from two different sources, the natural mineral from Scawt Hill, County Antrim, and the synthetic mineral from spiegeleisen slags. Both types of material have been fully deseribed by Tilley and Vincent (1948). Their analysis shows that the slag mineral is a calcium orthosilicate in which Ca is partly replaced by Mg, Mn, and Ba, the extent of the replacement being represented by the formula (Cal.59Ba0.08Mg0.31Mn0.09)SiO4. Tilley and Vincent conclude that this orthorhombic (pseudo-hexagonal) phase is identical with the high-temperature form α' of pure Ca2SiO4, the existence of which was suggested by Bredig (1943a), and confirmed by TrSmel (1949) using a high-temperature powder camera. Bredig (1943a) also suggests, on the basis of a comparison of X-ray powder patterns, that the crystal structure of α'-Ca2SiO4 is similar to that of β-K2SO4. The present single-crystal work was originally undertaken in order to investigate the structure of α'-Ca2SiO4 more fully.

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