quasi-crystal


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quasi-crystal

[¦kwä·zē ′krist·əl]
(crystallography)
A phase of solid matter that, like a crystal, exhibits long-range orientational order and translational order but whose atoms and clusters repeat in a sequence defined by a sum of periodic functions whose periods are in an irrational ratio.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The forbidden crystal was therefore termed quasi-crystal. It turned out that the crystalline structure of the quasi-crystal showed great resemblance to the structures Caris had created in his Polyhedral net structures in the early seventies (figure 6).
The fivefold symmetry in the quasi-crystal and the Polyhedral net structures by Caris can be compared to the fivefold symmetry in the so-called Penrose patterns (3).
Quasi-crystals were first discovered in 2984, by Shechtaman and his co-workers as a new class of crystal structures that are somewhere between the amorphous soilds and true crystals.
This gain in efficiency will be of particular interest to researchers for the determination of inorganic/organomettalic crystal structure, study of incommensurates and quasi-crystals, and powder anaylsis.
The morphology of the clay within these microaggregates is a characteristic associated with the clustering of quasi-crystals of smectite described by Oades and Waters (1991).
The morphology of the aggregate is characteristic of the clustering of quasi-crystals of clay.
The articles cover a broad spectrum of topics including high-pressure crystallography, magnetic structure determinations, quasi-crystals, novel biomaterials, biological minerals, structure determination via neutron and x-ray diffraction, reduced cells, standard reference materials, phase equilibria and ceramic oxides, crystallographic texture, zeolitic materials, near perfect crystals, electron diffraction, crystallographic databases, protein crystallography, crystallography in construction, and synchrotron radiation.
For example, the article on quasi-crystals strikes at the fundamental definition of a crystal lattice.
In his search for a design inventory which is free of human preconceptions, Eisenman has married Form Z Macintosh software to natural phenomena such as waves, quasi-crystals and slime moulds, all of which, in his terms, have no a priori knowledge or contingencies.
When in 1984 crystallographers were amazed to learn that a team of scientists had succeeded in producing crystalline complexes based on regular pentagons in a rapidly cooled manganese-aluminium alloy it was decided that these should be known as "pseudo-" or "quasi-crystals"; as the discovery was the result of a technically contrived process, it would have been scientifically incorrect to use the term "crystal" as if it were referring to a naturally occurring formation.
When, in 1984, complexes of regular pentagons were observed in a rapidly cooled alloy of aluminium and manganese for the first time, these were referred to as 'quasi-crystals', as they had been synthetically contrived by scientists.
Of the theoretical hypotheses brought forward so far to explain the occurrence of the quasi-crystals mentioned above some are of special importance, namely the ones suggesting the possibility of a gradual transition between the even-numbered dimensions, or, to put it differently, the ones implying that our reality is of a hyper-dimensional nature.
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