scholarly journals Crystal Structures of Piperazinium Tetrahalogenometallates (II) [C4H12N2]MX4 (M = Zn, Hg; X = Br, I)

2006 ◽  
Vol 61 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Ingrid Svoboda ◽  
Hartmut Fuess ◽  
Thorsten M. Gesing ◽  
...  
Keyword(s):  
Phase Transition ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Lattice Stability ◽  
Space Group ◽  
Hydrogen Bond Networks

The crystal structures of piperazinium tetrahalogenometallates (II) [C4H12N2]MX4(M = Zn, Hg; X = Br, I), orthorhombic with space group P212121 and Z = 4 are isostructural with [C4H12N2]CdI4. The structure consists of piperazinium cations and isolated tetrahedralMX4 anions. [C4H12N2]ZnBr4 (1): a = 850.4(2), b = 1146.5(3), and c = 1228.4(4) pm at 300(2) K, [C4H12N2]ZnI4 (2): a = 886.89(6), b = 1209.11(9), and c = 1293.79(9) pm at 223(2) K, [C4H12N2]HgBr4 (3): a = 865.48(14), b = 1158.7(3), and c = 1233.3(2) pm at 293(2) K, [C4H12N2]HgI4 (4): a = 899.6(2), b = 1230.0(2), and c = 1299.5(3) pm at 293(2) K. All crystals show a structural phase transition at about 560 K and decomposition temperatures above 600 K. The lattice stability of the crystals is well explained by N-H · · · X hydrogen bond networks.

Phase transition in metal–organic complex trans-PtCl2(PEt3)2 under pressure: insights into the molecular and crystal structure

CrystEngComm ◽  
2018 ◽  
Vol 20 (26) ◽  
pp. 3728-3740 ◽  
Author(s):  
Naini Bajaj ◽  
Himal Bhatt ◽  
K. K. Pandey ◽  
H. K. Poswal ◽  
A. Arya ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bond ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Molecular And Crystal Structure ◽  
Supramolecular Architecture ◽  
Organic Complex ◽  
Metal Organic Complex ◽  
Metal Organic

Molecular reorientations result in structural phase transition in trans-PtCl2(PEt3)2 under pressure, leading to a hydrogen bond assisted supramolecular architecture.

scholarly journals Disordered sodium alkoxides from powder data: crystal structures of sodium ethoxide, propoxide, butoxide and pentoxide, and some of their solvates

2021 ◽  
Vol 77 (1) ◽  
pp. 68-82
Author(s):  
Maurice Beske ◽  
Stephanie Cronje ◽  
Martin U. Schmidt ◽  
Lukas Tapmeyer
Keyword(s):  
Hydrogen Bond ◽  
Crystal Structures ◽  
Sodium Ethoxide ◽  
Amyl Alcohol ◽  
X Ray Diffraction ◽  
Oh Groups ◽  
Space Group ◽  
X Ray ◽  
Alkyl Groups ◽  
Hydrogen Bond Networks

The crystal structures of sodium ethoxide (sodium ethanolate, NaOEt), sodium n-propoxide (sodium n-propanolate, NaO n Pr), sodium n-butoxide (sodium n-butanolate, NaO n Bu) and sodium n-pentoxide (sodium n-amylate, NaO n Am) were determined from powder X-ray diffraction data. NaOEt crystallizes in space group P 421 m, with Z = 2, and the other alkoxides crystallize in P4/nmm, with Z = 2. To resolve space-group ambiguities, a Bärnighausen tree was set up, and Rietveld refinements were performed with different models. In all structures, the Na and O atoms form a quadratic net, with the alkyl groups pointing outwards on both sides (anti-PbO type). The alkyl groups are disordered. The disorder becomes even more pronounced with increasing chain length. Recrystallization from the corresponding alcohols yielded four sodium alkoxide solvates: sodium ethoxide ethanol disolvate (NaOEt·2EtOH), sodium n-propoxide n-propanol disolvate (NaO n Pr·2 n PrOH), sodium isopropoxide isopropanol pentasolvate (NaO i Pr·5 i PrOH) and sodium tert-amylate tert-amyl alcohol monosolvate (NaO t Am· t AmOH, t Am = 2-methyl-2-butyl). Their crystal structures were determined by single-crystal X-ray diffraction. All these solvates form chain structures consisting of Na+, –O− and –OH groups, encased by alkyl groups. The hydrogen-bond networks diverge widely among the solvate structures. The hydrogen-bond topology of the i PrOH network in NaO i Pr·5 i PrOH shows branched hydrogen bonds and differs considerably from the networks in pure crystalline i PrOH.

Structural evolution of a Ge-substituted SnSe thermoelectric material with low thermal conductivity

2018 ◽  
Vol 51 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Federico Serrano-Sánchez ◽  
Norbert M. Nemes ◽  
José Luis Martínez ◽  
Oscar Juan-Dura ◽  
Marco Antonio de la Torre ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Structural Evolution ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Low Thermal Conductivity ◽  
Structure Space

Thermoelectric materials are expected to become new alternative sources of sustainable energy. Among them, the SnSe intermetallic alloy has been described as an excellent thermoelectric compound, characterized by an extremely low thermal conductivity with maximum performance at the onset of a structural phase transition at 800 K. Recently, novel SnSe derivatives with Ge substitution have been synthesized by a direct arc-melting technique. This produces nanostructured polycrystalline samples that exhibit a record high Seebeck coefficient, anticipating an excellent performance above room temperature. Here, the structural phase transition from a GeS-type structure (space groupPnma) to a TlI-type structure (space groupCmcm) is investigatedin situ vianeutron powder diffraction (NPD) in the temperature range 298–853 K for the selected composition Sn0.8Ge0.2Se. This transition takes place at 803 K, as shown by differential scanning calorimetry. The analysis from the NPD data shows a non-monotonic behaviour of the anisotropic displacement parameters upon entering the domain of theCmcmstructure. The energies of the atomic vibrations have been quantitatively analysed by fitting the temperature-dependent mean-square displacements to Einstein oscillators. The thermal conductivity of Sn0.8Ge0.2Se is as low as 0.35 W m−1 K−1at 773 K, which mostly represents the lattice thermal contribution.

scholarly journals High-pressure study of Li[Li1/3Ti5/3]O4 spinel

2018 ◽  
Vol 5 (8) ◽  
pp. 1941-1949 ◽  
Author(s):  
Kazuhiko Mukai ◽  
Ikuya Yamada
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Lithium Ion Batteries ◽  
Crystal Structures ◽  
Structural Phase Transition ◽  
Electrode Materials ◽  
Structural Phase ◽  
Lithium Ion ◽  
High Pressure Study ◽  
Lithium Titanium

Crystal structures and electrochemical reactivities of high-pressure forms of the lithium titanium spinel Li[Li1/3Ti5/3]O4 (LTO) were investigated under a pressure of 12 GPa to elucidate its structural phase transition from spinel to post-spinel and to obtain a wide variety of electrode materials for lithium-ion batteries.

Isolated versus Condensed Anion Structure: the Influence of the Cation Size and Hydrogen Bond on Structure and Phase Transition in MX42- Complex Salts. 2,2-Dimethyl-1,3-propanediammonium Tetrabromocadmate(II) Monohydrate, Dimethylammonium Tetrabromozincate(II), and Dimethylammonium Tetrabromocadmate(II)

1996 ◽  
Vol 51 (9) ◽  
pp. 1027-1036 ◽  
Author(s):  
Hideta Ishihara ◽  
Shi-qi Dou ◽  
Keizo Horiuchi ◽  
V. G . Krishnan ◽  
Helmut Paulus ◽  
...  
Keyword(s):  
Phase Transition ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Distorted Tetrahedron ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Dimethyl Ammonium ◽  
Complex Salts ◽  
Cation Size

Abstract In the course of work on the anion condensation of Cd and Zn halides, the crystal structures and 79,81 Br NQR spectra of 2,2-dimethyl-1,3-propanediammonium tetrabromocadmate(II) monohydrate (1) and dimethylammonium tetrabromozincate(II) (2), and 79-81 Br NQR spectra of dimethyl-ammonium tetrabromocadmate(II) (3) have been studied. An isolated [CdBr4]2- ion of the salt [H3NCH2C(CH3)2CH2NH3 ]CdBr4 • H2O (1) is formed, with polar orthorhombic space group Pbc21, Z = 4, a = 645.5(3), b = 1628.3(8), c -1389.5(6) pm. [(CH3)2 NH2 ]2ZnBr4 (2) has also an isolated anion lattice, with monoclinic space group, P21 /c, Z = 4, a = 870.6(3), b = 1195.6(4), c = 1628.9(5) pm, β = 121.84(1)°. The 81 Br NQR spectrum of (1) is a quartet (ν in MHz, T = 77 K/ 303 K): ν1 = 68.403/64.278; ν2 = 65.296/62.663; ν3 = 56.525/54.660; V4 = 43.211/45.422. The 81 Br NQR spectrum of (2) is a quartet too (ν in MHz, T= 77 K/300 K): ν1 = 66.848/64.784; ν2= 63.152/ 61.883; ν3 = 57.498/55.890; ν4 = 49.416/50.224. The 81 Br NQR spectrum of [(CH3)2NH2 ]2CdBr4 (3) is also a quartet (ν in MHz, T =77 K/310 K): ν1 = 68.606/67.272; ν2 = 65.806/63.296; ν3 = 58.096/ 57.369; ν4 = 55.757/53.393. The change of NQR frequencies with temperature is smooth for all three compounds. One of the 81 Br NQR lines in both (1) and (2) increases slightly in frequency with increasing T. In the compound (1), the H2O coordinates to NH3+ groups and to bromines forming a distorted tetrahedron (Br...)2 ...H2O... (... HN)2 , the six angles lying between 69° and 131°. The relations between the bromine NQR and the crystal structures are discussed for the title compounds.

Crystal structure and structural phase transition in bismuth-containing HoFe3(BO3)4 in the temperature range 11–500 K

2019 ◽  
Vol 75 (6) ◽  
pp. 954-968 ◽  
Author(s):  
Ekaterina S. Smirnova ◽  
Olga A. Alekseeva ◽  
Alexander P. Dudka ◽  
Dmitry N. Khmelenin ◽  
Kirill V. Frolov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Local Environment ◽  
Atomic Displacement ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Atomic Displacement Parameters ◽  
Thermal Vibrations

An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3(BO3)4 between 11 and 500 K has revealed structural phase transition at T str = 365 K. The Bi atoms enter the composition from Bi2Mo3O12-based flux during crystal growth and significantly affect T str. The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96Bi0.04)Fe3(BO3)4. In the low-temperature (LT) phase below T str the (Ho0.96Bi0.04)Fe3(BO3)4 crystal symmetry is trigonal, of space group P3121, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32. There is a sharp jump of oxygen O1 (LT) and O2 (LT) atomic displacement parameters (ADP) at T str. O1 and O2 ADP ellipsoids are the most elongated over 90–500 K. In space group R32 specific distances decrease steadily or do not change with decreasing temperature. In space group P3121 the distortion of the polyhedra Ho(Bi)O6, Fe1O6 and Fe2O6, B2O3 and B3O3 increases with decreasing temperature, whereas the triangles B1O3 remain almost equilateral. All BO3 triangles deviate from the ab plane with decreasing temperature. Fe–Fe distances in Fe1 chains decrease, while distances in Fe2 chains increase with decreasing temperature. The Mössbauer study confirms that the FeO6 octahedra undergo complex dynamic distortions. However, all observed distortions are rather small, and the general change in symmetry during the structural phase transition has very little influence on the local environment of iron in oxygen octahedra. The Mössbauer spectra do not distinguish two structurally different Fe1 and Fe2 positions in the LT phase. The characteristic temperatures of cation thermal vibrations were calculated using X-ray diffraction and Mössbauer data.

Topological phase transition associated with structural phase transition in ternary half Heusler compound LiAuBi.

2022 ◽  
Author(s):  
Anita Yadav ◽  
Shailesh Kumar ◽  
Manoharan Muruganathan ◽  
Rakesh Kumar
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Topological Phase ◽  
Heusler Compound ◽  
Space Group ◽  
Topological Phase Transition ◽  
Lattice Space ◽  
Fcc Lattice

Abstract In this article, we report detailed theoretical investigations of topological phases in a new non-centrosymmetric half Heusler compound LiAuBi upto a pressure of 30 GPa. It is found that the compound forms into a dynamically stable face centered cubic (FCC) lattice structure of space group F ¯43m (216) at ambient pressure. The compound is topologically non-trivial at ambient pressure, but undergoes a quantum phase transition to trivial topological phase at 23.4 GPa. However, the detailed investigations show a structural phase transition from FCC lattice (space group 216) to a honeycomb lattice (space group 194) at 13 GPa, which is also associated with a non-trivial to trivial topological phase transition. Further investigations show that the compound also carries appreciable thermoelectric properties at ambient pressure. The figure of merit (ZT) increases from 0.21 at room temperature to a maximum value of 0.22 at 500K. The theoretical findings show its potential for practical applications in spintronics as well as thermoelectricity, therefore LiAuBi needs to be synthesized and investigated experimentally for its applications.

On the polymorphism of benzocaine; a low-temperature structural phase transition for form (II)

2009 ◽  
Vol 65 (4) ◽  
pp. 509-515 ◽  
Author(s):  
Eric J. Chan ◽  
A. David Rae ◽  
T. Richard Welberry
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Space Group ◽  
Polymorphic Forms ◽  
Similar Phase

A low-temperature structural phase transition has been observed for form (II) of benzocaine (BZC). Lowering the temperature doubles the b-axis repeat and changes the space group from P212121 to P1121 with γ now 99.37 °. The structure is twinned, the twin rule corresponding to a 21 screw rotation parallel to a. The phase transition is associated with a sequential displacement parallel to a of zigzag bi-layers of ribbons perpendicular to b*. No similar phase transition was observed for form (I) and this was attributed to the different packing symmetries of the two room-temperature polymorphic forms.

scholarly journals Reversible 3D-2D structural phase transition and giant electronic modulation in nonequilibrium alloy semiconductor, lead-tin-selenide

2021 ◽  
Vol 7 (12) ◽  
pp. eabf2725
Author(s):  
Takayoshi Katase ◽  
Yudai Takahashi ◽  
Xinyi He ◽  
Terumasa Tadano ◽  
Keisuke Ide ◽  
...  
Keyword(s):  
Phase Transition ◽  
Crystal Structures ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Three Dimensional ◽  
Alloy System ◽  
Closed Shell ◽  
Property Change ◽  
Lead Tin Selenide ◽  
Nonequilibrium Growth

Material properties depend largely on the dimensionality of the crystal structures and the associated electronic structures. If the crystal-structure dimensionality can be switched reversibly in the same material, then a drastic property change may be controllable. Here, we propose a design route for a direct three-dimensional (3D) to 2D structural phase transition, demonstrating an example in (Pb1−xSnx)Se alloy system, where Pb2+ and Sn2+ have similar ns2 pseudo-closed shell configurations, but the former stabilizes the 3D rock-salt-type structure while the latter a 2D layered structure. However, this system has no direct phase boundary between these crystal structures under thermal equilibrium. We succeeded in inducing the direct 3D-2D structural phase transition in (Pb1−xSnx)Se alloy epitaxial films by using a nonequilibrium growth technique. Reversible giant electronic property change was attained at x ~ 0.5 originating in the abrupt band structure switch from gapless Dirac-like state to semiconducting state.

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