scholarly journals Phase transition sequences in tetramethylammonium tetrachlorometallates by X-ray diffraction and spectroscopic measurements

2017 ◽  
Vol 73 (5) ◽  
pp. 844-855 ◽  
Author(s):  
Jack Binns ◽  
Garry J McIntyre ◽  
José A. Barreda-Argüeso ◽  
Jesús González ◽  
Fernando Aguado ◽  
...  
Keyword(s):  
Phase Transition ◽  
Point Group ◽  
Lone Pair ◽  
Group Symmetry ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Intermediate Phases ◽  
Increasing Temperature ◽  
First Time ◽  
Prototype Phase

The phase transition sequences of two members of the tetramethylammonium tetrachlorometallate(III) family of hybrid organic–inorganic salts have been determined and structurally characterized as a function of temperature for the first time. Unusually, a reduction in point-group symmetry with increasing temperature until reaching a cubic prototype phase is observed. Two additional intermediate phases are observed for Fe3+. First-principles calculations and the presence of short Cl...Cl contacts for Ga3+suggest the [GaCl4]−anion to be conformationally hindered due to stronger lone-pair–σ-hole interactions. The conformationally more flexible Fe3+structures show sublattice melting with the onset of rotational disorder in the [NMe4]+cations occurring 40 K below the corresponding onset of rotational disorder in the [FeCl4]−sublattice.

Phase Transformation in Titanium Nanoparticles from First Principles

2014 ◽  
Vol 213 ◽  
pp. 42-46
Author(s):  
Andrey N. Chibisov
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Phase Transformation ◽  
First Principles ◽  
Point Group ◽  
Group Symmetry ◽  
Point Group Symmetry ◽  
First Principles Calculations ◽  
Titanium Nanoparticles

We have used molecular dynamics and first-principles calculations to investigate the structure and agglomeration of Ti nanoparticles. The results indicate that Ti nanoclusters undergo a phase transition with a change of point group symmetry. In addition, we found that titanium nanocluster growth occurred along the [0001] direction.

Raman-Spektren von SnJ4, GeJ4, TiBr4 und TiJ4 in flüssiger und kristalliner Phase / Raman Spectra of SnJ4, GeJ4, TiBr4, and TiJ4 in the Liquid and Crystalline Phase

1970 ◽  
Vol 25 (12) ◽  
pp. 1374-1381 ◽  
Author(s):  
W. Kiefer ◽  
H. W. Schrötter
Keyword(s):  
Raman Spectra ◽  
Ruby Laser ◽  
Detection System ◽  
Point Group ◽  
Visible Region ◽  
Group Symmetry ◽  
Pure Liquid ◽  
Electronic Detection ◽  
Polarization Studies ◽  
First Time

The Raman spectra of four molecules absorbing in the visible region (SnJ4, GeJ4, TiBr4, and TiJ4) are presented. They were excited with a quasi-continuous ruby laser and recorded with a special electronic detection system. Except for TiJ4, complete Raman spectra of crystal powder pellets could be obtained for the first time. The assignment reported by previous authors was confirmed by accurate polarization studies of solutions or pure liquid. The assignment is also in the solid state possible on the basis of Td point group symmetry. The fundamental vibrations of TiJ4 in solutions are: ν1 (A1) =162, ν2 (E) =51, ν3 (F2) =319 and ν4 (F2) Y = 67 cm-1

X-ray diffraction and Raman study of DL-alanine at high pressure: revision of phase transitions

2012 ◽  
Vol 68 (4) ◽  
pp. 412-423 ◽  
Author(s):  
Nikolay A. Tumanov ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Group Symmetry ◽  
Second Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Raman Study

The effect of pressure on DL-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ∼ 6 GPa). No structural phase transitions have been observed. At ∼ 1.5–2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107–111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied.

Phase transitions of (1−x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions

1999 ◽  
Vol 14 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Jung-Kun Lee ◽  
Hyuk-Joon Youn ◽  
Kug Sun Hong
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Solutions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Phase Transition Temperatures ◽  
Temperature Phase Transition ◽  
Increasing Temperature

Morphotropic phase boundaries and temperature dependent phase transitions of (1 – x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions were investigated by x-ray diffraction, differential scanning calorimetry (DSC), and dielectric property analysis. Two morphotropic phase transitions at room temperature were found at x = 0.1 and 0.13, which were from antiferroelectric orthorhombic (with 4 × 4 × 2 superlattice [orthorhombic (I)]) to antiferroelectric orthorhombic (with 2 × 2 × 2 superlattice [orthorhombic (II)]) and from orthorhombic (II) to ferroelectric rhombohedral, respectively. With increasing temperature, the samples with 0.01 ≤ x < 0.1 showed two phase transitions, i.e., from orthorhombic (I) to orthorhombic (II) and from orthorhombic (II) to cubic. The other samples had only one phase transition with increasing temperature. Phase transition temperatures of all the samples were measured using DSC, and a phase diagram for the solid solutions was constructed. A model illustrating the antiparallel shift of Pb ions in the orthorhombic (II) phase was also proposed.

Structural Investigations of Colloidal Semiconductor Nanocrystal Heterostructures: Faceting and Epitaxy

1996 ◽  
Vol 452 ◽  
Author(s):  
A. V. Kadavanich ◽  
A. Mews ◽  
S. H. Tolbert ◽  
X. Peng ◽  
M. C. Schlamp ◽  
...  
Keyword(s):  
Point Group ◽  
Group Symmetry ◽  
X Ray Diffraction ◽  
Structural Investigations ◽  
Transmission Microscopy ◽  
Cds Quantum Dot ◽  
Show Evidence ◽  
Multi Wavelength ◽  
Heterogeneous Phase ◽  
Phase Proceeds

AbstractWe use High Resolution Transmission Microscopy (HRTEM) to study CdSe, CdS/HgS/CdS quantum-dot quantum well (QDQW), and CdSe/CdS core-shell nanocrystals, grown by wet-chemical techniques. The nanocrystals have faceted Wulff polyhedron shapes.In addition to HRTEM, we employ multi-wavelength anomalous dispersion (MAD) x-ray diffraction. We use computer modeling to help interpret the experimental data.Growth of a heterogeneous phase proceeds epitaxially preserving the overall shape and point-group symmetry of the original seed nanocrystals, both for wurtzite (CdSe/CdS) and zincblende (CdS/HgS/CdS) type structures.Recently prepared InAs nanocrystals also show evidence of faceting as observed by HRTEM and may lend themselves equally well to epitaxy.

scholarly journals Darstellung und Kristallstruktur von [(NH3)5Rh(H7O4)Rh(NH3)5](S2O6)2,5 · H2O (1). Ein gemischtes Aquopentamminrhodium(III)-hydroxopentamminrhodium(III)- dithionat mit einer neuartigen μ-H7O4-Struktureinheit / Preparation and Crystal Structure of [(NH3)5Rh(H7O4)Rh(NH3)5](S2O6)2,5 · H2O (1). A Mixed Aquopentaamminerhodium(III)-hydroxopentaamminerhodium(III) Dithionate with a Novel μ-H7O4 Structural Unit

1988 ◽  
Vol 43 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Walter Frank ◽  
Thomas Stetzer ◽  
Ludwig Heck
Keyword(s):  
Crystal Structure ◽  
Structural Unit ◽  
Small Difference ◽  
Point Group ◽  
Group Symmetry ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray

The title compound 1 can be obtained from an aqueous solution of aquopentaammine rhodium(III) dithionate and hydroxopentaammine rhodium(III) dithionate. The crystal structure has been determined from single crystal X-ray diffraction data and refined to R = 0.035 for 4390 unique reflections. Crystal data: monoclinic, space group P21/c, a = 1300.9(5) pm. b = 1472.3(6) pm. c = 1478.8(9) pm, β = 106.20(4)°, Z = 4.In the crystal dinuclear rhodium cations with point group symmetry 1 (C1) are found. A central μ-H3O2-bridge is formed by strong hydrogen bonding between aquo and hydroxo ligands; this bridge is additionally coordinated by two molecules of water. The entire bridging system is therefore H7O4-(H3O2- · 2 H2O). O-O distances characterizing the strength of the three hydrogen bonds within this new kind of structural unit are O(H2O-Rh 1)-O(HO-Rh2): 248 pm. O(H2O-Rh 1)-O(H2Oa): 273 pm, O(HO-Rh2)-O(H2Ob): 287 pm. The hydrogen atoms involved in these bridges have been located. The small difference in the Rh 1-O(H2O) - (205.4(3) pm) and Rh2-O(OH)- (204.3(3) pm) distances indicates that the entire H7O4-- moiety serves as a μ-bridging unit between Rh 1 and Rh 2

scholarly journals Redetermination of the crystal structure of caesium tetrafluoridobromate(III) from single-crystal X-ray diffraction data

IUCrData ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Artem V. Malin ◽  
Sergei I. Ivlev ◽  
Roman V. Ostvald ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Point Group ◽  
Group Symmetry ◽  
Site Symmetry ◽  
X Ray Diffraction ◽  
Cation Site ◽  
X Ray ◽  
Square Planar

Caesium tetrafluoridobromate(III), CsBrF4, was crystallized in form of small blocks by melting and recrystallization. The crystal structure of CsBrF4 was redetermined from single-crystal X-ray diffraction data. In comparison with a previous study based on powder X-ray diffraction data [Ivlev et al. (2013). Z. Anorg. Allg. Chem. 639, 2846–2850], bond lengths and angles were determined with higher precision, and all atoms were refined with anisotropic displacement parameters. It was confirmed that the structure of CsBrF4 contains two square-planar [BrF4]− anions each with point group symmetry mmm, and a caesium cation (site symmetry mm2) that is coordinated by twelve fluorine atoms, forming an anticuboctahedron. CsBrF4 is isotypic with CsAuF4.

Low-temperature phase transition in glycine–glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry

2012 ◽  
Vol 68 (3) ◽  
pp. 287-296 ◽  
Author(s):  
Boris A. Zakharov ◽  
Evgeniy A. Losev ◽  
Boris A. Kolesov ◽  
Valeri A. Drebushchak ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Glutaric Acid ◽  
Group Symmetry ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The occurrence of a first-order reversible phase transition in glycine–glutaric acid co-crystals at 220–230 K has been confirmed by three different techniques – single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P21/c to P\bar 1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

scholarly journals Observation of the shock-induced β-Sn to b.c.t.-Sn transition using time-resolved X-ray diffraction

2019 ◽  
Vol 26 (1) ◽  
pp. 96-101 ◽  
Author(s):  
R. Briggs ◽  
R. Torchio ◽  
A. Sollier ◽  
F. Occelli ◽  
L. Videau ◽  
...  
Keyword(s):  
Phase Transition ◽  
European Synchrotron Radiation Facility ◽  
Maximum Pressure ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Reverse Transition ◽  
First Time ◽  
Pressure Phase ◽  
Good Agreement

Time-resolved X-ray diffraction measurements have been carried out on dynamically compressed Sn up to a maximum pressure of ∼13 GPa at the European Synchrotron Radiation Facility. The phase transition from β-Sn to body-centered tetragonal (b.c.t.) Sn has been observed using synchrotron X-ray diffraction for the first time undergoing shock compression and release. Following maximum compression, the sample releases to lower pressures for several nanoseconds until the reverse transition occurs. The data are in good agreement with previous shock boundaries that indicate that the β-Sn phase is stable ∼2 GPa higher than the static boundary upon compression and the b.c.t.-Sn phase is stable ∼1 GPa lower upon release. The transition to the high-pressure phase reveals a loss of texture in the X-ray diffraction data from the `quasi' single-crystal β-Sn structure to a more powder-like Debye–Scherrer ring.

scholarly journals Group 11 Pincer Oxazoline Complexes

2021 ◽  
Author(s):  
Mahroo T. Seighalani
Keyword(s):  
Point Group ◽  
Diffraction Method ◽  
Binding Mode ◽  
Group Symmetry ◽  
Pincer Complexes ◽  
Pincer Ligands ◽  
Henry Reaction ◽  
X Ray Diffraction ◽  
Pincer Ligand ◽  
Nitroaldol Reaction

The synthesis and characterization of new copper pincer complexes via cyclometallation of potentially anionic pincer ligands with C1 point group symmetry is reported. All of these complexes have been characterized by single crystal X-ray diffraction method, which confirms the proposed tridentate binding mode of pincer ligand and the formation of an amido N-Cu bond. The reactivity of two of the complexes was investigated towards C-C bond formation reaction, notably the Henry reaction. One of the complexes, which was derived from the achiral pincer ligand, is shown to be a suitable catalyst for the Henry reaction under the standard conditions. The Henry or nitroaldol reaction is one of the organic reactions which affords a C-C bond. The product of this reaction is a β-nitro alcohol which is formed by addition of a nitroalkane to a carbonyl compound.

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