Study That Led to the Discovery of Rhombohedral Close Packing and Hexagonal Close Packing as Two New and Independent Lattices

2019 ◽  
Vol 11 (12) ◽  
pp. 1179-1186
Author(s):  
Mohammad Abdul Wahab ◽  
Khurram Mujtaba Wahab
Keyword(s):  
Ab Initio ◽  
Basal Plane ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
Hexagonal Close Packed

An ab-initio calculation of angles has been made between various directions on close packed basal plane with the tilted axis obtained by placing identical atoms on voids. Results obtained from simple calculations provide a lot of important information related to Rhombohedral Close Packed and Hexagonal Close Packed structures, effectively leading to their discovery as independent and genuine space lattices from close packed category of materials. En-route, we also propose a separate equation to calculate the angles between two given directions in the above mentioned close packed crystal systems. Modes of polytype formation in close packing of identical atoms is also briefly discussed.

scholarly journals Quantum confinement of molecular deuterium clusters in carbon nanotubes: ab initio evidence for hexagonal close packing

2017 ◽  
Vol 19 (42) ◽  
pp. 28621-28629 ◽  
Author(s):  
María Pilar de Lara-Castells ◽  
Andreas W. Hauser ◽  
Alexander O. Mitrushchenkov ◽  
Ricardo Fernández-Perea
Keyword(s):  
Carbon Nanotubes ◽  
Ab Initio ◽  
Quantum Confinement ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
Deuterium Clusters

This study shows ab initio evidence for hexagonal close packing of D2 molecules in carbon nanotubes, with a = 3.6 Å and .

Alkalimetall-Arsenide A3As7 Und Aas (A = K, Rb, Cs). Synthesen, Kristallstrukturen, Schwingungsspektren / Alkaline Metal Arsenides A3As7 and AAs (A = K, Rb, Cs). Preparation, Crystal Structure, Vibrational Spectroscopy

2002 ◽  
Vol 57 (9) ◽  
pp. 963-975 ◽  
Author(s):  
Franziska Emmerling ◽  
Caroline Röhr
Keyword(s):  
Crystal Structure ◽  
Raman Spectroscopy ◽  
Vibrational Spectroscopy ◽  
Structure Type ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
Alkaline Metal ◽  
Zintl Phases ◽  
X Ray ◽  
Hexagonal Close Packed

The title compounds were synthesized from the elements and characterized via single crystal x-ray studies and Raman spectroscopy. In the Zintl phases A3As7 (A = K, Rb, Cs) the As atoms form nortricyclene-analogous anions As37 with As-As distances ranging from 230 to 254 pm. The three compounds crystallizewithdifferent newstructure types containing different packings of theAs7 anions:K3As7 (orthorhombic, Pbca; a=1291.9(8), b = 2544.1(9), c=1537.7(16) pm) shows a double hexagonal close packing (ABAC stacking of planes of hexagonal close packed anions), Rb3 As7 (monoclinic, P21/c, a = 757.3(5), b = 1310.2(8), c = 2692.7(18) pm , β= 91.972(12)°) hows a hexagonal close packing (AB) and the Cs compound (orthorhombic, Pbca, a = 1022.8(5), b = 1317.6(7), c = 2195.2(11) pm) a cubic close packing (ABC) (also present in theHT-forms of the three compounds) respectively. The alkaline metalmonoarsenides AAs (A = K, Rb) crystallize with the NaP structure type (A = K/Rb: orthorhombic, P212121; a = 661.7(5) / 658.1(8), b = 688.8(6) / 691.6(8), c = 1197.3(10) / 1204.7(10) pm, Z = 8) with approximate fourfold screw axes 41 of As$ chains, whereas the crystal structure of CsAs (hexagonal, P¯62m, a = 1219.7(3), c = 1046.3(2) pm, Z = 18) contains three crystallographically independent three membered rings As33 with As-As distances of 243.0 to 247.5 pm

scholarly journals HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

2012 ◽  
Author(s):  
John D. Bess ◽  
Barbara H. Dolphin ◽  
James W. Sterbentz ◽  
Luka Snoj ◽  
Igor Lengar ◽  
...  
Keyword(s):  
Close Packing ◽  
Experimental Program ◽  
Hexagonal Close Packing ◽  
Pebble Bed

scholarly journals HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

2013 ◽  
Author(s):  
John D. Bess ◽  
Barbara H. Dolphin ◽  
James W. Sterbentz ◽  
Luka Snoj ◽  
Igor Lengar ◽  
...  
Keyword(s):  
Close Packing ◽  
Experimental Program ◽  
Hexagonal Close Packing ◽  
Pebble Bed

Observations on the Fine Structure of the Eyespot and Associated Organelles in the Dinoflagellate Glenodinium Foliaceum

1969 ◽  
Vol 5 (2) ◽  
pp. 479-493 ◽  
Author(s):  
J. D. DODGE ◽  
R. M. CRAWFORD
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Lamellar Body ◽  
Ventral Side ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
Osmiophilic Granules ◽  
Algal Groups ◽  
Posterior Direction ◽  
Microtubular System

The eyespot of the marine dinoflagellate Glenodinium foliaceum is a flattened orange structure, more or less trapezoid in shape with an anterior hook-like projection. It is situated on the ventral side of the organism in the vicinity of the flagellar bases at the anterior end of the sulcus. In the electron microscope the eyespot is seen to contain two layers of osmiophilic granules 80-200 nm in diameter which usually show hexagonal close-packing. The eyespot is surrounded by a triple-membraned envelope and is not connected to any other organelle. Adjacent to the eyespot is a distinctive organelle termed the ‘lamellar body’. This consists of a stack of up to 50 flattened vesicles or disks, each 16 nm thick and about 750 nm wide, the whole being orientated in an antero-posterior direction. The lamellae are continuous, at the ends of the stack, with rough endoplasmic reticulum and are joined together by occasional bridges at their edges. The bases of the two flagella lie just ventral to the lamellar body and from them roots arise which pass by the eyespot and join the subthecal microtubular system. The eyespot of Glenodinium is unique both in structure and the presence of the associated lamellar body. It differs from eyespots which have been described from other algal groups and also from the more complex ocellus found in certain dinoflagellates belonging to the order Warnowiaceae. The method by which the eyespot functions is discussed and it is suggested that unidirectional stimuli could be perceived by shading of the lamellar body.

Topological signatures and stability of hexagonal close packing and Barlow stackings

Soft Matter ◽  
2021 ◽  
Author(s):  
Georg Osang ◽  
Herbert Edelsbrunner ◽  
Mohammad Saadatfar
Keyword(s):  
Close Packing ◽  
Hexagonal Close Packing ◽  
X Ray ◽  
3D Rendering

3D rendering of the experimental packing obtained via X-ray CT. A cut-out section shows the bulk crystallisation and partially crystallised regions.

Synthese und Struktur von Nb0,89Fe0,93Te2 und Ta0,77Fe0,90Te2 / Synthesis and Structure of Nb0.89Fe0.93Te2 and Ta0.77Fe0.90Te2

1992 ◽  
Vol 47 (9) ◽  
pp. 1203-1212 ◽  
Author(s):  
Jörg Neuhausen ◽  
Karl-Ludwig Stork ◽  
Elisabeth Potthoff ◽  
Wolfgang Tremel
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Chemical Transport ◽  
Structure Type ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
X Ray ◽  
The Relationship

Nb0.89Fe0.93Te2 and Ta0.77Fe0.90Te2 were prepared by chemical transport reactions. The crystal structures of both compounds were determined using X-ray single crystal methods. The structures of the layer compounds Nb0.89Fe0.93Te2 (Pmna, Z = 2, a = 7.951(1) Å, b = 7.241(1) A, c = 6.233(1) Å) and Ta0.77Fe0.90Te2 (Pmna, Z = 2, a = 7.890(2) Å, b = 7.252(2) Å, c = 6.192(1) Å) are based on a hexagonal close packing of Te atoms. Approximately one-half of the octahedral holes in this packing are occupied by Nb (Ta) atoms, about one-quarter of the tetrahedral holes are occupied by Fe atoms. The relationship to the NiAs structure type is discussed.

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