Hexagonal prisms

Periodic cells used in computer simulations the cube, truncated octahedron, hexagonal prism and rhombic hedron. 

The truncated octahedron and the rhombic dodecahedron provide periodic cells that are approximately spherical and so may be more appropriate for simulations of spherical molecules. The distance between adjacent cells in the truncated octahedron or the rhombic df)decahedron is larger than the conventional cube for a system with a given number of particles and so a simulation using one of the spherical cells will require fewer particles than a comparable simulation using a cubic cell. Of the two approximately spherical cells, the truncated octahedron is often preferred as it is somewhat easier to program. The hexagonal prism can be used to simulate molecules with a cylindrical shape such as DNA. 

Of the five possible shapes, the cube/parallelepiped and the truncated octahedron have been most widely used, with some simulations in the hexagonal prism. The formulae used to translate a particle back into the central simulation box for these three shapes are given in Appendix 6.4. It may be preferable to use one of the more common periodic cells even if there are aesthetic reasons for using an alternative. This is because the expressions for calculating the images may be difficult and inefficient to implement, even though the simulation would use fewer atoms. 

Perchlorates. Iron(II) perchlorate hexahydrate [13922-23-8], Fe(C10 2 6H20, is prepared by dissolving iron in cold, dilute perchloric acid or by dissolving FeS in perchloric acid. It crystallizes in hygroscopic, light green hexagonal prisms which are stable in dry air and extremely soluble (0.978 g/mL H2O at 0°C) in water and alcohol. It is susceptible to air oxidation in aqueous solution and decomposes above 100°C. Yellow iron(III) perchlorate... 

Benzil. Ben il [134-81-6] (diphenylethanedione) is a yellow soHd that crystallines from alcohol in hexagonal prisms. Ben nil can be prepared by the oxidation of bennoin [579-44-2] (2-hydroxy-2-phenylacetophenone) (298,299), which is itself prepared by the self-condensation of bennaldehyde (300). Ben nil is commercially produced in Japan and is used as a uv resin curing sensitizer (301). It has also been suggested as a chigger repeUant (302). 

C-Toxiferine II. This base was obtained from curares from Urbana and Caracas, sometimes accompanied by toxiferine II (see below), and was isolated by a special method as the chloride, C20H25ON2CI, [a] -f- 72-1° (H2O). The picrate forms hexagonal prisms, m.p. 215° (dec.). 

The dilithium triimidochalcogenites [Ei2 E(N Bu)3 ]2 form dimeric structures in which two pyramidal [E(N Bu)3] dianions are bridged by four lithium cations to form distorted, hexagonal prisms of the type 10.13. A fascinating feature of these cluster systems is the formation of intensely coloured [deep blue (E = S) or green (E = Se)] solutions upon contact with air. The EPR spectra of these solutions (Section 3.4), indicate that one-electron oxidation of 10.13a or 10.13b is accompanied by removal of one Ei" ion from the cluster to give neutral radicals in which the dianion [E(N Bu)3] and the radical monoanion [E(N Bu)3] are bridged by three ions. ... 

Ferrous Picrate. [C6H2(N02)30] 2Fe, mw 513.15, N 16.38%, dark green powder which expld feebly at 315—20°. It was obtained by drying the octahydrate in a vac dessicator over sulfuric acid. Its impact sensitivity was 14-15" (vs 14" for TNT). The octahydrate was obtained by treating a hot coned aq soln of ferrous sulfate with Ba picrate yel hexagonal prisms which turned brown on standing impact sensitivity 36"... 

For example [in] = three atoms not coplanar with the central atom as in NH3 [12p = hexagonal prism. When lone electron pairs in polyhedra vertices are also counted, a symbolism in the following manner can be used [y/ — At] (same meaning as [in]), [i/r — 6o] (same as [5y]), [2y - 6o] (same as [4/]). 

The linking pattern of two zeolites is shown in Fig. 16.24. They have the /I-cage as one of their building blocks, that is, a truncated octahedron, a polyhedron with 24 vertices and 14 faces. In the synthetic zeolite A (Linde A) the /3-cages form a cubic primitive lattice, and are joined by cubes. j3-Cages distributed in the same manner as the atoms in diamond and linked by hexagonal prisms make up the structure of faujasite (zeolite X). 

Figure 4.3. Infrared spectra of the HY sample upon TMA adsorption and NH3 saturation evidencing OH in the supercages at 3637 cm1, OH in the sodalite units at 3548 cm-1 and OH in the hexagonal prism at 3501 cm-1 [54].

Instead of forming a cubane or a dimer the X-ray structural analysis of monosodiated di-tert-butylsilandiol reveals a hexagonal prism formed by the sodium and oxygen atoms of six molecules this structural element is stable even in the gaseous state [2]. 

The dilithium triimidochalcogenites [Li2 E(NtBu)3 ]2 form dimeric structures in which two pyramidal [H( N B li )3]2 dianions are bridged by four lithium cations to form distorted, hexagonal prisms of the type 59. 

Hexagonal phosphorus pentoxide, 29 49 Hexagonal prism lattice, 8 114t Hexagonal soap phase, 22 726, 727 mixed soap crystals in, 22 729 Hexagonal structure... 

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