scholarly journals Structural and vibrational properties of agrellite

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ekaterina Kaneva ◽  
Alexandr Bogdanov ◽  
Roman Shendrik
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Structural Models ◽  
Structural Features ◽  
Formation Mechanisms ◽  
X Ray Diffraction ◽  
Silicate Mineral ◽  
Channel System ◽  
X Ray ◽  
Small Channel

Abstract Agrellite, NaCa2Si4O10F, is a tubular silicate mineral which crystal structure is characterized by extended [Si8O20]8– tubes and has a two-dimensional channel system. The mineral is a representative of a complex silicate family which contains some structural voids but cannot be considered as microporous because of small channel widths. However, the channel system of such minerals is able to host single guest atoms, molecules or radicals which can affect their physical properties. Presently, the exact mechanism of such hosting is undetermined. However, such information could be quite useful for materials’ application as zeolites as well as for a better understanding of their formation mechanisms. In this work we couple X-ray diffraction, infrared (IR) spectroscopy and ab initio calculations to identify structural features in agrellite from Malyy Murun massif (Russia) caused by incorporation of either H2O or OH− into the channel system. We construct structural models of water-containing NaCa2Si4O10F and identified H2O positions. The derivation of H2O sites is based on simulation of IR-spectra. Infrared spectroscopy in combination with the ab initio calculation has proven to be an effective tool for the identification of the structural positions of hydroxyl anions (OH−) and neutral water groups (H2O) in minerals.

scholarly journals The structure of kaliophilite KAlSiO4, a long-lasting crystallographic problem

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1070-1083 ◽  
Author(s):  
Enrico Mugnaioli ◽  
Elena Bonaccorsi ◽  
Arianna E. Lanza ◽  
Erik Elkaim ◽  
Virginia Diez-Gómez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structural Features ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Channel System ◽  
X Ray ◽  
Cell Parameters ◽  
Peak Broadening ◽  
Structure Solution

Kaliophilite is a feldspathoid mineral found in two Italian magmatic provinces and represents one of the 12 known phases with composition close to KAlSiO4. Despite its apparently simple formula, the structure of this mineral revealed extremely complex and resisted structure solution for more than a century. Samples from the Vesuvius–Monte Somma and Alban Hills volcanic areas were analyzed through a multi-technique approach, and finally the crystal structure of kaliophilite was solved using 3D electron diffraction and refined against X-ray diffraction data of a twinned crystal. Results were also ascertained by the Rietveld method using synchrotron powder intensities. It was found that kaliophilite crystallizes in space group P3 with unit-cell parameters a = 27.0597 (16), c = 8.5587 (6) Å, V = 5427.3 (7) Å3 and Z = 54. The kaliophilite framework is a variant of the tridymite topology, with alternating SiO4 and AlO4 tetrahedra forming sheets of six-membered rings (63 nets), which are connected along [001] by sharing the apical oxygen atoms. Considering the up (U) and down (D) orientations of the linking vertex, kaliophilite is the first framework that contains three different ring topologies: nine (1-3-5) (UDUDUD) rings, six (1-2-3) (UUUDDD) rings and twelve (1-2-4) (UUDUDD) rings. This results in a relatively open (19.9 tetrahedra nm−3) channel system with multiple connections between the double six-ring cavities. Such a framework requires a surprisingly large unit cell, 27 times larger than the cell of kalsilite, the simplest phase with the same composition. The occurrence of some Na for K substitution (3–10%) may be related to the characteristic structural features of kaliophilite. Micro-twinning, pseudo-symmetries and anisotropic hkl-dependent peak broadening were also detected, and they may account for the elusive character of the kaliophilite crystal structure.

scholarly journals A Comparative X-ray Diffraction Study and Ab Initio Calculation on RU60358, a New Pyrethroid

2006 ◽  
Vol 7 (8) ◽  
pp. 255-265
Author(s):  
Fodil Hamzaoui ◽  
Abdelkader Chouaih ◽  
Philippe Lagant ◽  
Ouassila Belarbi ◽  
Gérard Vergoten
Keyword(s):  
Ab Initio ◽  
Diffraction Study ◽  
Ab Initio Calculation ◽  
X Ray Diffraction ◽  
X Ray

High-pressure powder x-ray diffraction experiments and ab initio calculation of Ti3AlC2

2009 ◽  
Vol 106 (1) ◽  
pp. 013519 ◽  
Author(s):  
Haibin Zhang ◽  
Xiang Wu ◽  
Klaus Georg Nickel ◽  
Jixin Chen ◽  
Volker Presser
Keyword(s):  
High Pressure ◽  
Ab Initio ◽  
Ab Initio Calculation ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals New Insights into the Crystal Chemistry of Elpidite, Na2Zr[Si6O15]·3H2O and (Na1+YCax□1−X−Y)Σ=2Zr[Si6O15]·(3−X)H2O, and Ab Initio Modeling of IR Spectra

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2160
Author(s):  
Alexander Bogdanov ◽  
Ekaterina Kaneva ◽  
Roman Shendrik
Keyword(s):  
Ir Spectra ◽  
Structural Models ◽  
Chemical Characterization ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Special Group ◽  
X Ray ◽  
Influence Of Water ◽  
Radioactive Species

Elpidite belongs to a special group of microporous zirconosilicates, which are of great interest due to their capability to uptake various molecules and ions, e.g., some radioactive species, in their structural voids. The results of a combined electron probe microanalysis and single-crystal X-ray diffraction study of the crystals of elpidite from Burpala (Russia) and Khan-Bogdo (Mongolia) deposits are reported. Some differences in the chemical compositions are observed and substitution at several structural positions within the structure of the compounds are noted. Based on the obtained results, a detailed crystal–chemical characterization of the elpidites under study was carried out. Three different structure models of elpidite were simulated: Na2ZrSi6O15·3H2O (related to the structure of Russian elpidite), partly Ca-replaced Na1.5Ca0.25ZrSi6O15·2.75H2O (close to elpidite from Mongolia), and a hypothetical CaZrSi6O15·2H2O. The vibration spectra of the models were obtained and compared with the experimental one, taken from the literature. The strong influence of water molecule vibrations on the shape of IR spectra of studied structural models of elpidite is discussed in the paper.

scholarly journals Quantifying the likelihood of structural models through a dynamically enhanced powder X‐ray diffraction protocol

2021 ◽  
Author(s):  
Sander Borgmans ◽  
Sven M.J. Rogge ◽  
Juul S. De Vos ◽  
Christian V. Stevens ◽  
Pascal Van Der Voort ◽  
...  
Keyword(s):  
Structural Models ◽  
X Ray Diffraction ◽  
X Ray

Mechanical and Structural Properties of Superhard TiAlSiN Coatings Deposited by Arc Ion Plating of Cylindrical Cathode

2014 ◽  
Vol 783-786 ◽  
pp. 1426-1431
Author(s):  
Wang Ryeol Kim ◽  
Min Chul Kwon ◽  
Jung Hoon Lee ◽  
Uoo Chang Jung ◽  
Won Sub Chung
Keyword(s):  
Structural Properties ◽  
Nitrogen Pressure ◽  
Structural Features ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ion Plating ◽  
Arc Current ◽  
Cathode Arc ◽  
Cathodic Arc ◽  
Tialsin Coating

TiAlSiN coatings were deposited on WC-Co metal by using a cathodic arc ion deposition method of cylindrical cathode. We used Ti / Al (50 / 50 at.%) arc target and silicon sputter target. The influence of the nitrogen pressure, TiAl cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The structural features of the films were investigation in detail using X-ray diffraction. And coatings were characterized by means of FE-SEM, nanoindentation, Scratch tester, Tribology tester, XRD and XPS. The hardness of the film reached 43 GPa at the cathode arc current of 230 A and decreased with a further increase of the arc current. And the adhesion of the film reached 34 N. The results showed that the TiAlSiN coating exhibited an excellent mechanical properties which application for tools and molds.

Inosose-Flüssigkristalle / Inosose Liquid Crystals

1990 ◽  
Vol 45 (7) ◽  
pp. 1084-1090 ◽  
Author(s):  
Klaus Praefcke ◽  
Bernd Kohne ◽  
Andreas Eckert ◽  
Joachim Hempel
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
High Temperature ◽  
Liquid Crystalline ◽  
Structural Features ◽  
Lyotropic Liquid Crystal ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Alkyl Chains

Six S,S-dialkyl acetals 2a-f of inosose (1), tripodal in structure, have been synthesized, characterized and investigated by optical microscopy and differential scanning calorimetry (d.s.c.). The four S,S-acetals 2c-f with sufficiently long alkyl chains are thermotropic liquid crystalline; 2 e and 2 f are even dithermomesomorphic. Each of these four inosose derivatives 2c-f exhibits monotropically a most likely cubic mesophase (MI); in addition 2e and 2f show enantiotropically a hexagonal mesophase (Hx) with a non-covalent, supramolecular H-bridge architecture. Whereas the nature of the optically isotropic mesophase MI needs further clarification the stable high temperature mesophase Hx of 2 e and 2 f has been established by a miscibility test using a sugar S,S-dialkyl acetal also tripodal in structure and with a Hx phase proved by X-ray diffraction, but in contrast to 2 with an acyclic hydrophilic part. Similarities of structural features between the Hx-phases of 2e and 2f as well as of other thermotropic and lyotropic liquid crystal systems are discussed briefly.

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