scholarly journals Crystal structure of the λ-Al13Fe4-type intermetallic (Al,Cu)13(Fe,Cu)4

IUCrData ◽  
2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Cong Liu ◽  
Changzeng Fan
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Structure Analysis ◽  
Structure Type ◽  
X Ray ◽  
X Ray Scattering ◽  
Iron Copper ◽  
Aluminium Copper ◽  
High Pressure Sintering ◽  
New Phase

An (Al,Cu)13(Fe,Cu)4phase of [trideca(aluminium/copper) tetra(iron/copper)] was obtained by the high-pressure sintering (HPS) process of a mixture with composition Al78Cu15Fe7. Structure analysis suggests that Cu atoms can replace both Al and Fe atoms. Such findings support previous anomalous X-ray scattering (AXS) results although deviate from other reports. The new phase adopts the λ-Al13Fe4structure type where Cu atoms partially occupy the 2cand 4isites for Al and Fe atoms, respectively, with occupancies of 0.233 (5) and 0.173 (16).

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 Crystal Structures of Al2Cu Revisited: Understanding Existing Phases and Exploring Other Potential Phases

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1037 ◽  
Author(s):  
Sai Wang ◽  
Changzeng Fan
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Single Crystal ◽  
First Principles ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Relationships ◽  
Al2cu Phase ◽  
High Pressure Sintering

When processing single crystal X-ray diffraction datasets for twins of Al2Cu sample synthesized by the high-pressure sintering (HPS) method, we have clarified why the crystal structure of Al2Cu was incorrectly solved about a century ago. The structural relationships between all existing Al2Cu phases, including the Owen-, θ-, θ’-, and Ω-Al2Cu phases, were investigated and established based on a proposed pseudo Al2Cu phase. Two potential phases have been built up by adjusting the packing sequences of A/B layers of Al atoms that were inherent in all existing Al2Cu phases. The mechanical, thermal, and dynamical stability of two such novel phases and their electronic properties were investigated by first-principles calculations.

X-ray powder crystal structure analysis of high pressure tungsten dioxide. On the information in weak reflections

1994 ◽  
Vol 209 (8) ◽  
Author(s):  
M. Sundberg ◽  
P.-E. Werner ◽  
I. P. Zibrov
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
X Ray

AbstractA high-pressure modification of tungsten dioxide (hp-WOIn the hp-WO

scholarly journals Crystal structure of Al2.95Cr0.59, a phase closely related to the η-phase in the binary Al–Cr system

IUCrData ◽  
2020 ◽  
Vol 5 (10) ◽  
Author(s):  
Xu Geng ◽  
Bin Wen ◽  
Changzeng Fan
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Chemical Composition ◽  
Structure Analysis ◽  
Monoclinic Phase ◽  
Site Occupation ◽  
Al Content ◽  
High Pressure Sintering ◽  
Close Relationship ◽  
Cr System

The monoclinic η-phase in the binary Al–Cr system was initially named by Bradley & Lu [Bradley & Lu (1937). J. Inst. Met. 60, 319–337] as having the composition Al11Cr2 (Al:Cr ratio = 5.5:1). Its crystal structure was later refined [Cao & Kuo (2008). J. Alloys Compd. 458, 30, 319–337] to have a slightly lower Al content (Al:Cr ratio = 5.16:1). In the present work, a monoclinic phase with composition Al2.95Cr0.59 (Al:Cr ratio = 5.04:1) was obtained by high-pressure sintering (HPS) of a stoichiometric Al11Cr2 mixture. Structure analysis of this phase, hereafter named η′, revealed a close relationship to the previously reported η-Al11Cr2 structure, but with different mixed-occupied sites. Five fully occupied sites exhibit refined site occupation factors of 0.899 (5), 0.984 (4), 0.977 (5), 0.946 (4) and 0.945 (4) for the corresponding Al atoms. Moreover, there are no split Al sites in the η′-structure as reported for the η-structure. The refined chemical composition of the η′-phase revealed that it comprises two Al atoms fewer and two Cr atoms more than the previously reported η-Al11Cr2 phase.

scholarly journals Crystal structure of the Al8Cr5-type intermetallic Al7.85Cr5.16

IUCrData ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Xu Geng ◽  
Bin Wen ◽  
Changzeng Fan
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Structure Analysis ◽  
High Pressure Sintering

An aluminium-deficient Al8Cr5-type intermetallic with formula Al7.85Cr5.16 (octaaluminium pentachromium) was uncovered when high-pressure sintering of a mixture with composition Al11Cr4 was carried out. Structure analysis reveals that there are three co-occupied positions with refined occupancy factors for Al atoms being 0.958, 0.772 and 1/2. The present phase is confirmed to be isotypic with the previously reported rhombohedral Al8Cr5 ordered phase [Bradley & Lu (1937). Z. Kristallogr. 96, 20–37] and structurally closely related to the disordered phases of rhombohedral Al16Cr9.5 and cubic Al8Cr5.

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