A new high-pressure strontium germanate, SrGe2O5

2016 ◽  
Vol 72 (10) ◽  
pp. 716-719 ◽  
Author(s):  
Akihiko Nakatsuka ◽  
Kazumasa Sugiyama ◽  
Makio Ohkawa ◽  
Osamu Ohtaka ◽  
Keiko Fujiwara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystals ◽  
Materials Science ◽  
Perovskite Phase ◽  
Structural Response ◽  
Cation Substitution ◽  
Electronic Conductor ◽  
Structural Responses ◽  
Oxygen Framework

The Sr–Ge–O system has an earth-scientific importance as a potentially good low-pressure analog of the Ca–Si–O system, one of the major components in the constituent minerals of the Earth's crust and mantle. However, it is one of the germanate systems that has not yet been fully examined in the phase relations and structural properties. The recent findings that the SrGeO3high-pressure perovskite phase is the first Ge-based transparent electronic conductor make the Sr–Ge–O system interesting in the field of materials science. In the present study, we have revealed the existence of a new high-pressure strontium germanate, SrGe2O5. Single crystals of this compound crystallized as a co-existent phase with SrGeO3perovskite single crystals in the sample recovered in the compression experiment of SrGeO3pseudowollastonite conducted at 6 GPa and 1223 K. The crystal structure consists of germanium–oxygen framework layers stacked along [001], with Sr atoms located at the 12-coordinated cuboctahedral site; the layers are formed by the corner linkages between GeO6octahedra and between GeO6octahedra and GeO4tetrahedra. The present SrGe2O5is thus isostructural with the high-pressure phases of SrSi2O5and BaGe2O5. Comparison of these three compounds leads to the conclusion that the structural responses of the GeO6and GeO4polyhedra to cation substitution at the Sr site are much less than that of the SrO12cuboctahedron to cation substitution at the Ge sites. Such a difference in the structural response is closely related to the bonding nature.

scholarly journals Vibrational anisotropy of <i>δ</i>-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering

2021 ◽  
Vol 33 (4) ◽  
pp. 485-502
Author(s):  
Johannes Buchen ◽  
Wolfgang Sturhahn ◽  
Takayuki Ishii ◽  
Jennifer M. Jackson
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystals ◽  
Vibrational Properties ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
X Ray ◽  
X Ray Scattering ◽  
The Mean ◽  
Vibrational Anisotropy

Abstract. The formation of high-pressure oxyhydroxide phases spanned by the components AlOOH–FeOOH–MgSiO2(OH)2 in experiments suggests their capability to retain hydrogen in Earth's lower mantle. Understanding the vibrational properties of high-pressure phases provides the basis for assessing their thermal properties, which are required to compute phase diagrams and physical properties. Vibrational properties can be highly anisotropic, in particular for materials with crystal structures of low symmetry that contain directed structural groups or components. We used nuclear resonant inelastic X-ray scattering (NRIXS) to probe lattice vibrations that involve motions of 57Fe atoms in δ-(Al0.87Fe0.13)OOH single crystals. From the recorded single-crystal NRIXS spectra, we calculated projections of the partial phonon density of states along different crystallographic directions. To describe the anisotropy of central vibrational properties, we define and derive tensors for the partial phonon density of states, the Lamb–Mössbauer factor, the mean kinetic energy per vibrational mode, and the mean force constant of 57Fe atoms. We further show how the anisotropy of the Lamb–Mössbauer factor can be translated into anisotropic displacement parameters for 57Fe atoms and relate our findings on vibrational anisotropy to the crystal structure of δ-(Al,Fe)OOH. As a potential application of single-crystal NRIXS at high pressures, we discuss the evaluation of anisotropic thermal stresses in the context of elastic geobarometry for mineral inclusions. Our results on single crystals of δ-(Al,Fe)OOH demonstrate the sensitivity of NRIXS to vibrational anisotropy and provide an in-depth description of the vibrational behavior of Fe3+ cations in a crystal structure that may motivate future applications of NRIXS to study anisotropic vibrational properties of minerals.

scholarly journals Ge0.57Ti0.43O2: a new high-pressure material with rutile-type crystal structure

2018 ◽  
Vol 74 (7) ◽  
pp. 1010-1012 ◽  
Author(s):  
Emil Stoyanov ◽  
Kurt Leinenweber ◽  
Thomas L. Groy ◽  
Abds-Sami Malik
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
High Pressure ◽  
Single Crystals ◽  
Structure Type ◽  
Site Symmetry ◽  
Rutile Structure ◽  
High Pressure And Temperature ◽  
Atom Position ◽  
Type Crystal

Single crystals of a GeO2–TiO2 solid solution with the corresponding composition Ge0.57Ti0.43O2 (germanium titanium tetraoxide) were obtained by devitrification of germania-titania glass at high pressure and temperature. The new compound crystallizes in the rutile structure type (space group P42/mnm), where Ge and Ti share the same position M (site symmetry m.mm), with occupancy values of 0.57 (3) and 0.43 (3), respectively, and one O-atom position (m.2m). The M site is in a sixfold O-atom coordination and, as in the original TiO2 rutile structure, an elongation of the O—M—O bonds along the c-axis direction of the coordination polyhedron and deviation of the angles from 90° lead to a decrease in the coordination symmetry from octahedral to tetragonal. The Ge and Ti atoms are fully disordered in the structure, which indicates that the rutile structure is surprisingly pliant given the differing sizes of the two cations.

Die Kristallstruktur von α-ΚΖnΡΟ4 / The Crystal Structure of α-KZnPO4

1992 ◽  
Vol 47 (9) ◽  
pp. 1249-1254 ◽  
Author(s):  
Martina Andratschke ◽  
Klaus-Jürgen Range ◽  
Heinz Haase ◽  
Ulrich Klement
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Low Temperature ◽  
Single Crystals ◽  
Potassium Ions ◽  
Space Group ◽  
Temperature Modification ◽  
Type Apparatus

Single crystals of a-KZnPO4, the low-temperature modification of potassium zinc orthophosphate, were obtained from KZnPO4 powder by high pressure experiments in a modified Belt-type apparatus. The crystals are hexagonal, space group P 63, with a = 18.155(2), c = 8.504(1) Å, c/a = 0.4684 and Z = 24. The crystal structure, refined from diffractometer data to R = 0.077, Rw = 0.068, comprises an ordered network of ZnO4 and PO4 tetrahedra with rings of six tetrahedra vertical to the c-axis. The potassium ions are located in cavities formed by the rings.

scholarly journals A computational–experimental approach for automated crystal structure solution

2014 ◽  
Vol 70 (a1) ◽  
pp. C131-C131
Author(s):  
Chris Wolverton
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Hydrogen Storage ◽  
First Principles ◽  
Materials Science ◽  
Hybrid Approach ◽  
X Rays ◽  
Experimental Conditions ◽  
Algorithmic Optimization ◽  
Structure Solution

Crystal structure solution from diffraction experiments is one of the most fundamental tasks in materials science, chemistry, physics and geology. Unfortunately, numerous factors render this process labour intensive and error prone. Experimental conditions, such as high pressure or structural metastability, often complicate characterization. Furthermore, many materials of great modern interest, such as batteries and hydrogen storage media, contain light elements such as Li and H that only weakly scatter X-rays. Finally, structural refinements generally require significant human input and intuition, as they rely on good initial guesses for the target structure. To address these many challenges, we demonstrate a new hybrid approach, first-principles-assisted structure solution (FPASS), which combines experimental diffraction data, statistical symmetry information and first-principles-based algorithmic optimization to automatically solve crystal structures. We demonstrate the broad utility of FPASS to clarify four important crystal structure debates: the hydrogen storage candidates MgNH and NH3BH3; Li2O2, relevant to Li–air batteries; and high-pressure silane, SiH4.

scholarly journals Structural response of α-quartz under plate-impact shock compression

2020 ◽  
Vol 6 (35) ◽  
pp. eabb3913
Author(s):  
Sally June Tracy ◽  
Stefan J. Turneaure ◽  
Thomas S. Duffy
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Shock Compression ◽  
Materials Science ◽  
Metastable Phase ◽  
Dynamic Compression ◽  
Phase Region ◽  
High Pressure Phase ◽  
Gas Gun ◽  
Pressure Phase

Because of its far-reaching applications in geophysics and materials science, quartz has been one of the most extensively examined materials under dynamic compression. Despite 50 years of active research, questions remain concerning the structure and transformation of SiO2 under shock compression. Continuum gas-gun studies have established that under shock loading quartz transforms through an assumed mixed-phase region to a dense high-pressure phase. While it has often been assumed that this high-pressure phase corresponds to the stishovite structure observed in static experiments, there have been no crystal structure data confirming this. In this study, we use gas-gun shock compression coupled with in situ synchrotron x-ray diffraction to interrogate the crystal structure of shock-compressed α-quartz up to 65 GPa. Our results reveal that α-quartz undergoes a phase transformation to a disordered metastable phase as opposed to crystalline stishovite or an amorphous structure, challenging long-standing assumptions about the dynamic response of this fundamental material.

Notizen: Zur Kristallstruktur von SrPbO3 / The Crystal Structure of SrPbO3

1975 ◽  
Vol 30 (3-4) ◽  
pp. 277-278 ◽  
Author(s):  
Hans-L. Keller ◽  
Karl-H. Meier ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Pressure Synthesis ◽  
Group D

Single crystals of SrPbO3 could be prepared by oxygen-high-pressure-synthesis (PO2 &gt; 3500 at, t = 450°C). Single crystal X-ray diffraction data confirm the space group D2h16-Pnma. SrPbO3 belongs to the orthorhombic distorted Perowskit type with a = 5.964, b = 8.320, c = 5.860 Å. The atomic positions were refined.

Synthesis and Characterization of a Cubic Iron Hydroxy Boracite

2011 ◽  
Vol 66 (2) ◽  
pp. 107-114 ◽  
Author(s):  
Stephanie C. Neumair ◽  
Johanna S. Knyrim ◽  
Oliver Oeckler ◽  
Reinhard Kaindl ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Single Crystals ◽  
Room Temperature ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure High Temperature

The cubic iron hydroxy boracite Fe3B7O13OH・1.5H2O was synthesized from Fe2O3 and B2O3 under high-pressure/high-temperature conditions of 3 GPa and 960 °C in a modified Walker-type multianvil apparatus. The crystal structure was determined at room temperature by X-ray diffraction on single crystals. It crystallizes in the cubic space group F4̄3c (Z = 8) with the parameters a = 1222.4(2) pm, V = 1.826(4) nm3, R1 = 0.0362, and wR2 = 0.0726 (all data). The B-O network is similar to that of other cubic boracites.

scholarly journals Die Kristallstruktur von TIZnPO4 und TIZnAsO4 / The Crystal Structure of TIZnPO4 and TIZnAsO4

1994 ◽  
Vol 49 (9) ◽  
pp. 1282-1288 ◽  
Author(s):  
Martina Andratschke ◽  
Klaus-Jürgen Range ◽  
Claudia Weigl ◽  
Ulrike Schießl ◽  
Franz Rau
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystals ◽  
Structure Type ◽  
Monoclinic System ◽  
Space Group ◽  
High Pressure Synthesis ◽  
Pressure Synthesis ◽  
Derivatives Of ◽  
Type Apparatus

Single crystals of the title com pounds were obtained by high pressure synthesis in a modified Belt type apparatus. The compounds crystallize in the monoclinic system (space group P21) with a = 8.732(2), b = 5.468(1), c = 8.841(2) Å, β = 90.61(2)° for TlZnPO4 and a = 8.921(3), b = 5.631(1), c = 8.958(3) Å, β = 91.03(2)° for TlZnAsO4, Z = 4. The structures were refined from diffractom eter data to R = 0.072, Rw = 0.050 for 3700 (TlZnPO4) and to R = 0.093, Rw = 0.067 for 3943 (TlZnAsO4) independent absorption corrected reflections. The compounds are isotypic and belong to the “stuffed derivatives" of the Icmm structure type with a (ZnXO4)- network of alternating corner linked ZnO4 and XO4 tetrahedra (X = P, As) forming channels of six-membered rings in the direction of the a axis. These cavities contain two crystallographically independent Tl cations in an irregular coordination by eight nearest oxygen atoms

scholarly journals Die Kristallstruktur von Mangantetrafluorid The Crystal / Structure of Manganese Tetrafluoride

1987 ◽  
Vol 42 (9) ◽  
pp. 1102-1106 ◽  
Author(s):  
Bernd G. Müller ◽  
Michael Serafin
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystals ◽  
Lattice Energy ◽  
Space Group ◽  
Dark Blue

Single crystals of dark blue MnF4 have been obtained by high pressure fluorination (pF2 = 3 kbar) of MnF2. There exist two modifications: α-MnF4 crystallizes tetragonally body centered with a = 12.63(1), c = 6.049(5) Å, space group I41/a-C4h6 (No. 88). Z = 16; the structure of β-MnF4, (probably) rhombohedral with a = 19.56(2). c = 13.00(1) Å, Z = 72, is yet unknown in detail. MnF4 is paramagnetic with ,μeff (301.2 K) = 3.87 B. M. . The Curie-Weiss law is obeyed down to 22.4 K; the Madelung Part of lattice energy (MAPLE) is calculated to be 2475 kcal/mol.

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