Vacancy pairing and superstructure in the high-pressure silicate K1.5Mg2Si2O7H0.5: a new potential host for potassium in the deep Earth

2016 ◽  
Vol 72 (6) ◽  
pp. 822-827 ◽  
Author(s):  
M. D. Welch ◽  
L. Bindi ◽  
V. Petříček ◽  
J. Plášil
Keyword(s):  
Solid Solution ◽  
High Pressure ◽  
Structure Type ◽  
Stability Field ◽  
X Ray Diffraction ◽  
Cell Parameters ◽  
Limited Solid Solution ◽  
Distinct Structure ◽  
Single Structure ◽  
End Members

The high-pressure silicate K1.5Mg2Si2O7H0.5, synthesized and characterized by Welchet al.[(2012),Am. Mineral.97, 1849–1857], has been re-examined with the aim of determining the nature of the superstructure noted in their study. The composition corresponds to a 1:1 combination of KMg2Si2O7H and K2Mg2Si2O7end-members, but it is not a solid solution. Single-crystal X-ray diffraction data for one of the original K1.5Mg2Si2O7H0.5crystals synthesized at 16 GPa/1573 K, has been collected using a much longer exposure time in order to improve the intensity statistics of weak superlattice reflections identified by Welchet al.(2012). The superstructure has been determined using a superspace approach as having the superspace groupCmcm(0,β,0)00sandt0= 1/16 with refined parametersa= 8.7623 (10),b= 5.0703 (7),c= 13.2505 (11) Å,V= 588.69 (12) Å3. This structure corresponds to one with the conventional space groupPbnmand unit-cell parametersa= 8.7623 (10),b= 20.281 (3),c= 13.2505 (11) Å,V= 2354.7 (5) Å3and is based upon a super-sheet motif in which ordering involves rows of pairs of vacant interlayer K sites. This is the third topologically distinct structure type for the KMg2Si2O7H−K2Mg2Si2O7join and suggests that there is very limited solid solution, and so it can be expected that each of the three structures (P63cm, P\bar 3 1m andPbnm) has its own stability field, rather than being part of a continuous compositional series based upon a single structure type. As such, K1.5Mg2Si2O7H0.5should be considered as a potentially significant host of K in the Earth's mantle.

Synthesis and crystal structure of (Ag,Pd)22Se6

2013 ◽  
Vol 28 (1) ◽  
pp. 13-17 ◽  
Author(s):  
F. Laufek ◽  
A. Vymazalová ◽  
D.A. Chareev ◽  
A.V. Kristavchuk ◽  
J. Drahokoupil ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Glass Tube ◽  
Structure Type ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Cell Parameters ◽  
Silica Glass Tube

The (Ag,Pd)22Se6 phase was synthesized from individual elements by silica glass tube technique and structurally characterized from powder X-ray diffraction data. The (Ag,Pd)22Se6 phase crystallizes in Fm$\overline3$m symmetry, unit-cell parameters: a = 12.3169(2) Å, V = 1862.55(5) Å3, Z = 4, and Dc = 10.01 g/cm3. The crystal structure of the (Ag,Pd)22Se6 phase represents a stuffed 3a.3a.3a superstructure of the Pd structure (fcc), where only 4 from 108 available octahedral holes are occupied. Its crystal structure is related to the Cr23C6 structure type.

scholarly journals Redetermination of Sr2PdO3 from single-crystal X-ray data

2019 ◽  
Vol 75 (1) ◽  
pp. 30-32
Author(s):  
Gohil S. Thakur ◽  
Hans Reuter ◽  
Claudia Felser ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Structure Type ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Cell Parameters ◽  
Anisotropic Displacement Parameters

The crystal structure redetermination of Sr2PdO3 (distrontium palladium trioxide) was carried out using high-quality single-crystal X-ray data. The Sr2PdO3 structure has been described previously in at least three reports [Wasel-Nielen & Hoppe (1970). Z. Anorg. Allg. Chem. 375, 209–213; Muller & Roy (1971). Adv. Chem. Ser. 98, 28–38; Nagata et al. (2002). J. Alloys Compd. 346, 50–56], all based on powder X-ray diffraction data. The current structure refinement of Sr2PdO3, as compared to previous powder data refinements, leads to more precise cell parameters and fractional coordinates, together with anisotropic displacement parameters for all sites. The compound is confirmed to have the orthorhombic Sr2CuO3 structure type (space group Immm) as reported previously. The structure consists of infinite chains of corner-sharing PdO4 plaquettes interspersed by SrII atoms. A brief comparison of Sr2PdO3 with the related K2NiF4 structure type is given.

scholarly journals Redetermination of the crystal structure of RhPb2 from single-crystal X-ray diffraction data, revealing a rhodium deficiency

2021 ◽  
Vol 77 (12) ◽  
Author(s):  
Takashi Mochiku ◽  
Yoshitaka Matsushita ◽  
Nikola Subotić ◽  
Takanari Kashiwagi ◽  
Kazuo Kadowaki
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structure Type ◽  
Site Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Anisotropic Displacement Parameters ◽  
Slight Deficiency

RhPb2 (rhodium dilead) is a superconductor crystallizing in the CuAl2 structure type (space group I4/mcm). The Rh and Pb atoms are located at the 4a (site symmetry 422) and 8h (m.2m) sites, respectively. The crystal structure is composed of [RhPb8] antiprisms, which share their square faces along the c axis and the edges in the direction perpendicular to the c axis. We have succeeded in growing single crystals of RhPb2 and have re-determined the crystal structure on basis of single-crystal X-ray diffraction data. In comparison with the previous structure studies using powder X-ray diffraction data [Wallbaum (1943). Z. Metallkd. 35, 218–221; Havinga et al. (1972). J. Less-Common Met. 27, 169–186], the current structure analysis of RhPb2 leads to more precise unit-cell parameters and fractional coordinates, together with anisotropic displacement parameters for the two atoms. In addition and likewise different from the previous studies, we have found a slight deficiency of Rh in RhPb2, leading to a refined formula of Rh0.950 (9)Pb2.

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.

The solid solution TbNiIn1−x Ga x

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Myroslava Horiacha ◽  
Galyna Nychyporuk ◽  
Rainer Pöttgen ◽  
Vasyl Zaremba
Keyword(s):  
Solid Solution ◽  
Unit Cell ◽  
Type Structure ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Structure Space ◽  
Arc Melting

Abstract Phase formation in the solid solution TbNiIn1−x Ga x at 873 K was investigated in the full concentration range by means of powder X-ray diffraction and EDX analysis. The samples were synthesized by arc-melting of the pure metals with subsequent annealing at 873 K for one month. The influence of the substitution of indium by gallium on the type of structure and solubility was studied. The solubility ranges have been determined and changes of the unit cell parameters were calculated on the basis of powder X-ray diffraction data: TbNiIn1–0.4Ga0–0.6 (ZrNiAl-type structure, space group P 6 ‾ 2 m $P‾{6}2m$ , a = 0.74461(8)–0.72711(17) and c = 0.37976(5)–0.37469(8) nm); TbNiIn0.2–0Ga0.8–1.0 (TiNiSi-type structure, space group Pnma, а = 0.68950(11)–0.68830(12), b = 0.43053(9)–0.42974(6), с = 0.74186(10)–0.73486(13) nm). The crystal structures of TbNiGa (TiNiSi type, Pnma, a = 0.69140(5), b = 0.43047(7), c = 0.73553(8) nm, wR2=0.0414, 525 F 2 values, 21 variables), TbNiIn0.83(1)Ga0.17(1) (ZrNiAl type, P 6 ‾ 2 m $P‾{6}2m$ , a = 0.74043(6), c = 0.37789(3) nm, wR2 = 0.0293, 322 F 2 values, 16 variables) and TbNiIn0.12(2)Ga0.88(2) (TiNiSi type, Pnma, a = 0.69124(6), b = 0.43134(9), c = 0.74232(11) nm, wR2 = 0.0495, 516 F 2 values, 21 variables) have been determined. The characteristics of the solid solutions and the variations of the unit cell parameters are briefly discussed.

High-pressure study of a nanostructured SnSe1−xSx (x = 0.5) solid solution by in-situ X-ray diffraction and ab-initio calculations

2019 ◽  
Vol 792 ◽  
pp. 536-542
Author(s):  
Larissa da Silva Marques ◽  
Joelma Maria de Oliveira Ferreira ◽  
Querem Hapuque Félix Rebelo ◽  
Angsula Ghosh ◽  
Daniela Menegon Trichês ◽  
...  
Keyword(s):  
Solid Solution ◽  
High Pressure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure Study

A full-pattern fitting algorithm for energy-dispersive X-ray diffraction

2003 ◽  
Vol 36 (5) ◽  
pp. 1123-1127 ◽  
Author(s):  
Yu-Hui Dong ◽  
Jing Liu ◽  
Yan-Chun Li ◽  
Xiao-Dong Li
Keyword(s):  
High Pressure ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Fitting Algorithm ◽  
Diffraction Angle ◽  
Data Points ◽  
Diffraction Peaks ◽  
Very High

A full-pattern fitting algorithm for energy-dispersive X-ray diffraction is proposed, especially for high-pressure X-ray diffraction studies. The algorithm takes into account the errors in measuring the energy and the diffraction angle. A lognormal function is introduced to represent the background. All the peaks that are detectable in the diffraction spectra, including fluorescence and diffraction peaks, are considered together. Because all the data points in the spectra are used, the accuracy of the cell parameters obtained by this method is very high. This is very helpful in the analysis of the equation of state and the identification of new phases under high pressure.

X-Ray Diffraction Intensity of Oxife Soild Soultions: Application to Qualitative and Quantitative Phase Analysis

1982 ◽  
Vol 26 ◽  
pp. 119-128 ◽  
Author(s):  
Ronald C. Gehringer ◽  
Gregory J. McCarthy ◽  
R.G. Garvey ◽  
Deane K. Smith
Keyword(s):  
Phase Analysis ◽  
Solid Solutions ◽  
Inorganic Materials ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Qualitative And Quantitative ◽  
Quantitative Analyses ◽  
End Members

Solid solutions are pervasive in minerals and in industrial inorganic materials. The analyst is often called upon to provide qualitative and quantitative X-ray phase analysis for specimens containing solid solutions when all that is available are Powder Diffraction File (PDF) data or commercial standards for the end members. In an earlier paper (1) we presented several examples of substantial errors in accuracy of quantitative analysis that can arise when the crystallinity and composition of the analyte standard do not match those of the analyte in the sample of interest. We recommended that to obtain more accurate quantitative analyses, one should determine the analyte composition (e.g., from XRF on grains seen in a SEM or from comparison of cell parameters with those of the end members) and synthesize an analyte standard with this composition and with a crystallinity approximating that of the analyte (e.g., as determined from peak breadth or α1/ α2 splitting).

scholarly journals High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 910
Author(s):  
Daniel Diaz-Anichtchenko ◽  
Robin Turnbull ◽  
Enrico Bandiello ◽  
Simone Anzellini ◽  
Daniel Errandonea
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

Sign in / Sign up

Export Citation Format

Share Document