THE CRYSTAL STRUCTURE AND PHASE TRANSITIONS OF β-Zn2P2O7

1965 ◽  
Vol 43 (5) ◽  
pp. 1147-1153 ◽  
Author(s):  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Oxygen Atom ◽  
Bond Angle ◽  
Thermal Motion ◽  
Mirror Plane ◽  
Red Emission ◽  
Space Group ◽  
Central Oxygen ◽  
Cation Coordination

β-Zn2P2O7 crystallizes in the C2/m space group with lattice parameters a = 6.61 ± 0.01 Å, b = 8.29 ± 0.01 Å, c = 4.51 ± 0.01 Å, β = 105.4° ± 0.2° and z = 2. The anion, P2O7−4, is centered with its mirror plane coinciding with the mirror plane of the space group. The central oxygen atom, however, shows high anisotropic thermal motion and thus it appears that the P—O—P bond angle is linear only as a result of thermal averaging. The cations are found on twofold axes in irregular sixfold coordination and these ZnO6 groups share three edges with neighboring cations. This cation coordination is, therefore, consistent with that predicted from the red emission of β-Zn2P2O7:Mn++.

REFINEMENT OF THE CRYSTAL STRUCTURE OF β-Mg2P2O7

1965 ◽  
Vol 43 (5) ◽  
pp. 1139-1146 ◽  
Author(s):  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Bond Angle ◽  
Analysis Data ◽  
Thermal Motion ◽  
Infrared Studies ◽  
Central Oxygen ◽  
Atomic Parameters

The crystal structure of Mg2P2O7 reported by Lukaszewicz has been refined by least squares analysis. Data of the hkl type with O ≤ k ≤ 6 have been used to obtain improved atomic parameters. The central oxygen atom of the P2O7−4 is found to have enhanced thermal motion in the plane perpendicular to the P—P vector. Thus the P—O—P bond angle appears to be linear in this phase because of a thermal averaging of the position of the central oxygen atom. This conclusion is in agreement with that obtained by Lazarev from infrared studies.

scholarly journals Crystal structure of β-Zn3(PO4)2

1967 ◽  
Vol 45 (20) ◽  
pp. 2303-2316 ◽  
Author(s):  
J. S. Stephens ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Lattice Parameters ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Basic Cation ◽  
Cation Coordination ◽  
Oxygen Atoms

β-Zn3(PO4)2 crystallizes in the monoclinic space group P 21/c with lattice parameters, a = 9.393(3) Å, b = 9.170(6) Å, c = 8.686(3) Å, β = 125.73(10)°, and Z = 4. The three independent cations are strongly ligated to 4, 5, and 5 oxygen atoms, with average Zn—O bond distances of 1.98 ± 0.09 Å, 2.10 ± 0.10 Å, and 2.08 ± 0.13 Å respectively. In addition there are two longer Zn—O distances of 2.51 Å and 2.55 Å in this structure. The PO4 groups exist as independent, nearly regular tetrahedra, with each oxygen atom ligated to two cations. Unlike the structures found for the α and γ phases of Zn3(PO4)2, which contain ribbons and sheets respectively as the basic cation coordination motif, the structure of β-Zn3(PO4)2 contains interconnected sheets.

Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

Crystal structure of Cd2V2O7

1967 ◽  
Vol 45 (20) ◽  
pp. 2297-2302 ◽  
Author(s):  
P. K. L. Au ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Lattice Parameters ◽  
The Other ◽  
Distorted Octahedron ◽  
Thermal Activity ◽  
Space Group ◽  
Bond Angles ◽  
Central Oxygen ◽  
Oxygen Atoms

Cadmium pyrovanadate crystallizes in the C2/m space group with lattice parameters a = 7.088(5) Å, b = 9.091(5) Å, c = 4.963(5) Å, β = 103°21(5)′, and z = 2. This crystal is an isostructure of the mineral thortveitite and thus the anion consists of a pair of centrosymmetrically related corner-sharing VO4 tetrahedra while the cation resides within a distorted octahedron of oxygen atoms. The anion has a linear V—O—V group, but, as with the isostructural pyrophosphates, the central oxygen atom shows an anomalously high thermal activity. The V—O bond distances are 1.76 Å for the inner bond and 1.70 Å for the terminal bond. The bond angles about the anion and cation are similar to those found for the other analogues of thortveitite.

The crystal structure of kalsilite, KAlSiO4

1965 ◽  
Vol 35 (272) ◽  
pp. 588-595 ◽  
Author(s):  
A. J. Perrotta ◽  
J. V. Smith
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Crystal Structures ◽  
Bond Angle ◽  
Three Dimensional ◽  
Full Matrix ◽  
Ideal Position ◽  
Wide Range ◽  
The Ideal

SummaryA full-matrix, three-dimensional refinement of kalsilite, KAlSi04 (hexagonal, a 5·16, c 8.69 Å, P6a), shows that the silicon and aluminium atoms are ordered. The respective tetrahedral distances of 1·61 and 1·74 Å agree with values of 1·61 and 1·75 Å taken to be typical of framework structures. As in nepheline, an oxygen atom is statistically distributed over three sites displaced 0·25 Å from the ideal position on a triad axis. This decreases the bond angle from 180° to 163° in conformity with observations on some other crystal structures. The potassiumoxygen distances of 2·77, 2·93, and 2·99 Å are consistent with the wide range normally found for this weakly bonded atom.

Darstellung und Kristallstruktur von Lithiumozonid-Ammoniakat (1/5) LiO3 · 5 NH3/Synthesis and Crystal Structure of Lithiumozonide-Ammonia (1/5) LiO3 · 5 NH3

1999 ◽  
Vol 54 (11) ◽  
pp. 1345-1349 ◽  
Author(s):  
Wilhelm Klein ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Cation Exchange ◽  
Liquid Ammonia ◽  
Boiling Temperature ◽  
Synthesis And Crystal Structure ◽  
Central Oxygen

Lithium ozonide has been synthezised starting from cesium ozonide via cation exchange in liquid ammonia and crystallizes at -78°C as an ammoniate, LiO3 · 5NH3. The coarse, ruby red crystals decompose above the boiling temperature of ammonia and are extremely sensitive to moisture. The crystal structure of L iO3 · 5NH3 (P c21n; a = 1231.9(5), b = 637.4(2), c = 1104.8(4) pm; Z = 4; R1 = 4.57%; 1318 independent reflections) consists of lithium tetramine complexes, ozonide anions and non coordinating ammonia molecules. With respect to the arrangement of the complex cations and of the anions there is similarity to the WC type of structure. The central oxygen atom of the ozonide anion is disordered.

Nitrido-und Oxochlorokomplexe des Vanadiums(V); die Kristallstruktur von AsPh4 [V0C14] Nitrido and Oxochloro Complexes of Vanadium(V); the Crystal Structure of AsPh4[VOCl4]

1980 ◽  
Vol 35 (5) ◽  
pp. 522-525 ◽  
Author(s):  
Gisela Beindorf ◽  
Joachim Strähle ◽  
Wolfgang Liebelt ◽  
Kurt Dehnicke
Keyword(s):  
Crystal Structure ◽  
Ir Spectra ◽  
Bond Length ◽  
Bond Angle ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Linear Arrangement ◽  
Space Group ◽  
X Ray ◽  
Complex Anions

The complexes AsPh4[Cl4V = N-Cl] and AsPh4[VOCl4] are prepared by the reaction of AsPh4Cl with Cl3VNCl and VOCl3, respectively. The IR spectra indicate C4v symmetry for the complex anions with multiple VN and VO bonds and a linear arrangement for the VNCl-group. AsPh4[VOCl4] crystallizes in the tetragonal space group P4/n with two formula units in the unit cell. The crystal structure was solved by X-ray diffraction methods (R = 0,062, 1096 observed, independent reflexions). The structure consists of AsPh4+ cations and [VOCl4]- anions with symmetry C4v. The extremely short VO bond length corresponds with a VO triple; its steric requirements cause the relatively large bond angle OVCl of 103.4°.

79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide

1989 ◽  
Vol 44 (1) ◽  
pp. 41-55 ◽  
Author(s):  
Jutta Hartmann ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Temperature Range

Abstract The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.

Synthesen und Kristallstrukturen von [PPh3Me]NO2 und [PPh3 Me]HCO2H2O / Syntheses and Crystal Structures of [PPh3Me]NO2 and [PPh3Me]HCO2H2O

1988 ◽  
Vol 43 (10) ◽  
pp. 1279-1284 ◽  
Author(s):  
Mervat El Essawi ◽  
H Gosmann ◽  
D Fenske ◽  
F Schmock ◽  
K Dehnicke
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Ir Spectra ◽  
Bond Angle ◽  
Water Molecules ◽  
Moist Air ◽  
Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
Structure Determinations

Triphenylmethylphosphonium nitrite and formate have been prepared by the reaction of [PPh3Me]I with silver nitrite, and lead formate, respectively, in aqueous solutions. [PPh3Me]NO2 (1) forms pale yellow crystals, and [PPh3Me]HCO2·H2O (2) forms white crystals. Both compounds are soluble in water, ethanol, and dichloromethane. In moist air 2 is hydrated to yield [PPh3Me]HCO2·2H2O (3). The compounds were characterized by their IR spectra, 1 and 2 also by X-ray crystal structure determinations.[PPh3Me]NO2 (1): space group P21/n, Z = 4, 2088 independent observed reflexions, R = 0.062. Lattice dimensions (20 °C): a = 914.7(3), b = 1887.5(9), c = 1080.0(4) pm, β = 110.29(3)°. The compound consists of PPh3Me+ ions and NO2- anions with bond lengths of 114.2(6) pm and a bond angle of 124.1(7)°. [PPh3Me]HCO2·H2O (2): space group P21/n, Z = 4, 2973 independent observed reflexions, R = 0.069. Lattice dimensions (-20 °C): a = 931(2), b = 1558(3), c = 1281(2) pm, β = 105.9(1)°. The compound consists of PPh3Me+ ions and formate anions which form centrosymmetric dimeric units [HCO2·H2O]22- through hydrogen bridges of the water molecules. Bond lengths CO 122.4(4) and 120.9(4) pm. bond angle OCO 129.9(4)°.

Oxofluoro-oxalato-vanadate des vierwertigen Vanadins: Schwingungsspektrum und Struktur von Na3[VOF(C2O4)2] • 6 H2O.

1976 ◽  
Vol 31 (5) ◽  
pp. 537-540 ◽  
Author(s):  
Helmut Rieskamp ◽  
Rainer Mattes
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Fluorine Atom ◽  
Direct Methods ◽  
Terminal Oxygen Atom ◽  
Triclinic Space Group ◽  
Trans Effect ◽  
Space Group ◽  
X Ray ◽  
In Cis

The Na and NH4 salts of the [VOF(C2O4)2]3--ion have been prepared. The crystal structure of the former has been determined from X-ray diffractometer data. The crystals are triclinic, space group P with Z = 2. The structure was solved by `direct methods' and refined to R 0.050 for 1749 reflections. In the anion, vanadium(IV) is octahedrally coordinated by a terminal oxygen atom, a fluorine atom in cis-position to the former, and two bidentate oxalate ligands. The terminal V—O-bond exhibits a strong ‘trans’ effect.

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