Topotactic, pressure-driven, diffusion-less phase transition of layered CsCoO2 to a stuffed cristobalite-type configuration

2019 ◽  
Vol 75 (4) ◽  
pp. 704-710
Author(s):  
Naveed Zafar Ali ◽  
Branton J. Campbell ◽  
Martin Jansen
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Three Dimensional ◽  
Phase Cell ◽  
Ambient Conditions ◽  
Space Group ◽  
Layered Architecture ◽  
Β Phase ◽  
Vertex Sharing ◽  
Two Phases

CsCoO2, featuring a two-dimensional layered architecture of edge- and vertex-linked CoO4 tetrahedra, is subjected to a temperature-driven reversible second-order phase transformation (α → β) at 100 K, which corresponds to a structural relaxation with concurrent tilting and breathing modes of edge-sharing CoO4 tetrahedra. In the present investigation, it was found that pressure induces a phase transition, which encompasses a dramatic change in the connectivity of the tetrahedra. At 923 K and 2 GPa, β-CsCoO2 undergoes a first-order phase transition to a new quenchable high-pressure polymorph, γ-CsCoO2. It is built up of a three-dimensional cristobalite-type network of vertex-sharing CoO4 tetrahedra. According to a Rietveld refinement of high-resolution powder diffraction data, the new high-pressure polymorph γ-CsCoO2 crystallizes in the tetragonal space group I41/amd:2 (Z = 4) with the lattice constants a = 5.8711 (1) and c = 8.3214 (2) Å, corresponding to a shrinkage in volume by 5.7% compared with the ambient-temperature and atmospheric pressure β-CsCoO2 polymorph. The pressure-induced transition (β → γ) is reversible; γ-CsCoO2 stays metastable under ambient conditions, but transforms back to the β-CsCoO2 structure upon heating to 573 K. The transformation pathway revealed is remarkable in that it is topotactic, as is demonstrated through a clean displacive transformation track between the two phases that employs the symmetry of their common subgroup Pb21 a (alternative setting of space group No. 29 that matches the conventional β-phase cell).

Bulk modulus and high-pressure crystal structures of tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 determined by X-ray powder diffraction

2000 ◽  
Vol 56 (2) ◽  
pp. 310-316 ◽  
Author(s):  
Robert E. Dinnebier ◽  
Stefan Carlson ◽  
Sander van Smaalen
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Crystal Structures ◽  
Phase Iii ◽  
Ambient Conditions ◽  
Space Group ◽  
X Ray ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 (TC) (P < 16.0 GPa, T = 298 K) is reported using high-resolution angle-dispersive X-ray powder diffraction. The compound has crystal structures with the molecules in a cubic-close-packed (c.c.p.) arrangement. It shows three phase transitions in the measured pressure range. At ambient conditions, TC has space group Fm{\bar 3}m (Z = 4) with a = 12.8902 (2) Å, V = 2141.8 (1) Å3 (phase I). Between 0 and 0.13 GPa TC exhibits a first-order phase transition into a structure with space group Pa{\bar 3} (phase II). A second first-order phase transition occurs between 0.2 and 0.28 GPa into a structure with space group P213 (phase III). Under non-hydrostatic pressure conditions (P > 10  GPa) a transformation is observed into a c.c.p. structure that is different from the face-centred-cubic structure at ambient conditions. A non-linear compression behaviour is observed, which could be described by a Vinet relation in the range 0.28–4.8 GPa. The extrapolated bulk modulus of the high-pressure phase III was determined to be K 0 = 7.1 (8) GPa. The crystal structures in phase III are refined against X-ray powder data measured at several pressures between 0.49 and 4.8 GPa, and the molecules are found to be fully ordered. This is interpreted to result from steric interactions between neighbouring molecules, as shown by analysing the pressure dependence of intramolecular angles, torsion angles and intermolecular distances. Except for their cell dimensions, phases I, II and III are found to be isostructural to the corresponding phases at low temperatures.

scholarly journals Crystal and electronic structure engineering of tin monoxide by external pressure

2021 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
High Pressures ◽  
Low Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

AbstractAlthough tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (β-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than α-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa. Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO → α-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0–9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

scholarly journals High pressure γ-to-β phase transition in bulk and nanocrystalline In2Se3

2016 ◽  
Vol 36 (4) ◽  
pp. 549-556 ◽  
Author(s):  
Anya M. Rasmussen ◽  
Elham Mafi ◽  
Wenguang Zhu ◽  
Yi Gu ◽  
Matthew D. McCluskey
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Β Phase

A tetragonal polymorph of SrMn2P2made under high pressure – theory and experiment in harmony

2017 ◽  
Vol 46 (21) ◽  
pp. 6835-6838 ◽  
Author(s):  
Weiwei Xie ◽  
Michał J. Winiarski ◽  
Tomasz Klimczuk ◽  
R. J. Cava
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Tetragonal Phase ◽  
Ambient Pressure ◽  
Structure Type ◽  
Space Group ◽  
Type Space ◽  
Tetragonal Phase Transition ◽  
Theory And Experiment

A trigonal–tetragonal phase transition in SrMn2P2is proposed and confirmed experimentally under high pressure. At ambient pressure, SrMn2P2crystallizes in the primitive trigonal La2O3structure type (space groupP3̄m1) in blue. Under high pressure, the tetragonal ThCr2Si2structure type (space groupI4/mmm) in red is more stable.

Spontaneous deformation of protocatechuic acid monohydrate crystals: crystallographic aspects

1983 ◽  
Vol 387 (1793) ◽  
pp. 311-330 ◽  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Protocatechuic Acid ◽  
Crystal Structure Analysis ◽  
Stable Phase ◽  
Space Group ◽  
Molecular Arrangement ◽  
Two Phases

Remarkable aspects of the crystallization of 3,4-dihydroxybenzoic acid (protocatechuic acid, PCA) from water as described by R. W. Wood ( Proc. R. Soc. Lond . A 197,283-294 (1949)) are confirmed. This compound crystallizes as the monohydrate in four different polymorphic phases: three are triclinic (oblique needles, needles and rhombs) and belong to one subgroup, while the fourth, monoclinic, phase constitutes a separate subgroup. It is probable that the triclinic rhombs are the stable phase at 25° C, with the other phases monotropically related to it. Crystal data for the triclinic needles are a = 9.926(9), b = 9.532(9), c = 8.131(8)Å, α = 100.8(1), β = 90.7(1), γ = 102.4(1)°, Z = 4, space group P1 - ; and for th e triclinic rhombs a = 12.693(9), b = 8.011(6), c = 8.121(6) Å, α = 72.2(1), β = 108.5(1), γ = 103.2(1)°, Z = 4, space group P1 - . Both crystals can be described in terms of a unit cell containing eight formula units, with dimensions a ≈ 12.7, b ≈ 9.5, c ≈ 13.0 Å, α ≈ 88, β ≈ 101, γ ≈ 107°; the space group for the triclinic needles is B1 - and for the triclinic rhombs A1 - . Crystal structure analyses (four-circle diffractometer, MoKα) of these two phases (triclinic needles, 1287 reflexions used in the final refinement cycle, R F = 11.1%; triclinic rhombs, 1761 reflexions, R F = 6.9%) show that both contain essentially similar layer pairs of PCA and H 2 O molecules, with hydrogen bonding both within each layer and, apparently, between them; however, the stacking of the layer pairs in the two phases differs. The crystals of the oblique needles are so small and unstable to stress that crystal structure analysis was not possible. The crystal structure of the monoclinic needles ( a = 12.32(1), b = 3.64(1), c = 17.60(2) Å, β = 107.7(2)°, Z = 4, space group P2 1 / n was determined (CuK α , 787 reflexions, R F = 6.8%); the overall molecular arrangement differs from that in the triclinic phases in an absence of PCA•H 2 O layers although there are distinct resemblances between the hydrogen bonding schemes. The phase transition ‘oblique needles → triclinic needles’ is ‘single crystal to single crystal’ and is a topotaxic transition. The phase transition ‘triclinic needles → triclinic rhombs’ is ‘single crystal to oriented polycrystal’ and is described as partially topotaxic, there being preservation of layer arrangement but not of complete three-dimensional orientation.

Synthesis and Characterization of the Manganese Borate α-MnB2O4

2011 ◽  
Vol 66 (9) ◽  
pp. 882-888
Author(s):  
Stephanie C. Neumair ◽  
Lukas Perfler ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Lattice Parameters ◽  
Synthesis And Characterization ◽  
Manganese Ions ◽  
Space Group ◽  
Dimensional Network ◽  
Oxygen Atoms

The high-pressure manganese borate α-MnB2O4 was synthesized under high-pressure/hightemperature conditions of 6.5 GPa and 1100 ◦C in a modified Walker-type multianvil apparatus. The monoclinic compound is isotypic to α-FeB2O4, CaAl2O4-II, CaGa2O4, andβ -SrGa2O4 crystallizing with eight formula units in the space group P21/c (Z = 8) with the lattice parameters a = 712.1(2), b = 747.1(2), c = 878.8(2) pm, β = 94.1(1)◦, V = 0.466(1) nm3, R1 = 0.0326, and wR2 = 0.0652 (all data). The compound is built up from layers of “sechser” rings of corner-sharing BO4 tetrahedra that are interconnected to a three-dimensional network. The manganese ions are coordinated by seven oxygen atoms and situated in channels along the a axis.

Phase transitions of BaCO3 at high pressures

2008 ◽  
Vol 72 (2) ◽  
pp. 659-665 ◽  
Author(s):  
S. Ono ◽  
J. P. Brodholt ◽  
G. D. Price
Keyword(s):  
Phase Transition ◽  
Experimental Study ◽  
High Pressure ◽  
Phase Transitions ◽  
Bulk Modulus ◽  
First Principles ◽  
High Pressures ◽  
Ambient Conditions ◽  
The Stability ◽  
Previous Experimental Study

AbstractFirst-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropicc ompressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

scholarly journals Phase transition and structures of the twinned low-temperature phases of (Et4N)[ReS4]

2020 ◽  
Vol 76 (3) ◽  
pp. 231-235
Author(s):  
Eduard Bernhardt ◽  
Regine Herbst-Irmer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Title Compound ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Rapid Cooling ◽  
Space Group ◽  
Disordered Structure ◽  
Β Phase ◽  
Α Phase

The title compound, tetraethylammonium tetrathiorhenate, [(C2H5)4N][ReS4], has, at room temperature, a disordered structure in the space group P63 mc (Z = 2, α-phase). A phase transition to the monoclinic space group P21 (Z = 2, γ-phase) at 285 K leads to a pseudo-merohedral twin. The high deviation from the hexagonal metric causes split reflections. However, the different orientations could not be separated, but were integrated using a large integration box. Rapid cooling to 110–170 K produces a metastable β-phase (P63, Z = 18) in addition to the γ-phase. All crystals of the β-phase are contaminated with the γ-phase. Additionally, the crystals of the β-phase are merohedrally twinned. In contrast to the α-phase, the β- and γ-phases do not show disorder.

scholarly journals Crystal and Electronic Structure Engineering of Tin Monoxide by External Pressure

2020 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
Low Pressure ◽  
External Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

Abstract Although tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressure through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (A-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than l-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to t-SnO at around 120 GPa. Our work also reveals that h-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase o-SnO for the phase transition path Pnma-SnO ®u-SnO ® g-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize h-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of -SnO can be engineered in a low-pressure range (0-9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

Room-Temperatrue Structure and Geometrical Analysis of the Cubic–Tetragonal Phase Transition in Dodecasil 3C-THF

1997 ◽  
Vol 53 (1) ◽  
pp. 18-24 ◽  
Author(s):  
K. Knorr ◽  
W. Depmeier
Keyword(s):  
Phase Transition ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Group Symmetry ◽  
Ambient Conditions ◽  
Space Group ◽  
Symmetry Properties ◽  
Ideal Framework ◽  
Tetragonal Phase Transition ◽  
The Ideal

The structure of dodecasil 3C-tetrahydrofuran [Si68O136]·4M, M = (CH2)4O, at room temperature was determined from a merohedrally twinned crystal in the tetragonal space group I41/a. The deformation of the ideal framework at the cubic tetragonal phase transition at T c ≃ 365 K could be explained mainly by two different symmetry-breaking processes. (i) A tetragonal tetrahedron distortion of the Si(5) tetrahedra and (ii) a hitherto unknown local one-dimensional tilt mechanism, localized in the tetrahedral network. The location of the axes of this tilt system coincides with the positions of the fourfold inversion axes in the space group I41/a. At room temperature the tilt angle is = 24°. The symmetry properties of the tilt system can explain the reduction of space-group symmetry from the space group of the ideal structure Fd\overline 3m to the space group at ambient conditions I41/a. The guest molecule tetrahydrofuran does not fit the cage symmetry and has been found to be dynamically disordered. The average structure shows an off-center location in the [51264] cage and follows the local \overline 4symmetry of the cage.

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