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Kasper Structures (kasper + structure)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Space fullerenes: a computer search for new Frank,Kasper structures

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2010
Mathieu Dutour Sikiri
A Frank,Kasper structure is a 3-periodic tiling of the Euclidean space by tetrahedra such that the vertex figure of any vertex belongs to four specified patterns with, respectively, 20, 24, 26 and 28 faces. Frank,Kasper structures occur in the crystallography of metallic alloys and clathrates. A new computer enumeration method has been devised for obtaining Frank,Kasper structures of up to 20 cells in a reduced fundamental domain. Here, the 84 obtained structures have been compared with the known 27 physical structures and the known special constructions by Frank,Kasper,Sullivan, Shoemaker,Shoemaker, Sadoc,Mosseri and Deza,Shtogrin. [source]

The self-hosting structure of ,-Ta

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2002
Alla Arakcheeva
Using electrodeposition from a bath of molten fluorides, single crystals of tetragonal ,-tantalum have been obtained for the first time at normal pressure. The unit-cell parameters are a = 10.211,(3), c = 5.3064,(10),Å, space group P21m. The ,-Ta structure belongs to the ,-type Frank,Kasper structures which are typical for binary intermetallic compounds and ,-U. In comparison to the ,-type, additional intercalated Ta atoms (population factor ,0.01) have been detected between the atoms located in the channels of the structure. The shorter interatomic distances observed between the channel atoms in comparison with the atoms of the framework justify the `self-hosting' characteristic. ,-Ta exhibits common features with the complex tetragonal structures of the high-pressure phases for the elements Rb, Ba, Sr, Bi and Sb. [source]