bipyramid


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bipyramid

[¦bī¦pir·ə‚mid]
(crystallography)
A crystal having the form of two pyramids that meet at a plane of symmetry. Also known as dipyramid.
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An important special case is the proper bipyramid [-1, 1] [direct sum] Q over Q.
Tellurite oxide is characterized by two major structural configuration units: trigonal bipyramid (Te[O.sub.4] and trigonal pyramid (Te[O.sub.3]).
Meanwhile, tellurite oxide can be divided into two types of structural configuration units that are trigonal bipyramid, Te[O.sub.4], and trigonal pyramid, Te[O.sub.3].
An introduction of fluorine into Te[O.sub.2]-based glass system results in reduction of Te-O-Te linkages due to a gradual transformation of trigonal bipyramid TeO4 (tbp) through TeO3+1 to trigonal pyramid TeO3 decreasing the connectivity of the tellurite glass former network.
The [Al.sub.6] and [Al.sub.7] clusters have a distorted tetragonal bipyramid ([D.sub.2d]) and an antitrigonal prism with a capping atom ([C.sub.3v]), respectively.
Example 3.3 Consider the equatorial bipyramid: the two-dimensional simplicial complex B with vertices [5] and facets 123, 124, 125, 134, 135, 234, 235.
The pseudocrystals, to 3.5 cm, are dull milky white but textbook-sharp, composed about equally of a tetragonal prism and a tetragonal bipyramid, with small basal pinacoid faces topping (and bottoming) off the shape.
The bond pair 1551, corresponding to a pentagonal bipyramid, is the characteristic of icosahedral order.
Sb(III) ion is five-coordinated by two amido N atoms and three carboxyl O atoms from a single [Hedta.sup.3-] ligand, forming a distorted trigonal bipyramid geometry.
The bond pair 1551, 1541, and 1431, corresponding to a pentagonal bipyramid, is the characteristic of icosahedral order.
Tellurite oxide consists of two types of structural configuration units, that is, trigonal bipyramid, Te[O.sub.4] and trigonal pyramid, Te[O.sub.3].
Forms include a first-order and second-order prism, two first-order bipyramids, one second order bipyramid and the basal pinacoid.