Structure orthorhombic

The dehydration and interconversion reactions of the various forms of calcium sulphate [dihydrate, hemihydrate (a and 3 pseudo morphs) and anhydrous salt (hexagonal and orthorhombic structures)] have been studied by Ball et al. [281,590,591] who compared their observations with the available rate and microscopic data. The important features of the complicated behaviour found are summarized in the scheme [281]... 

AlSCl has an orthorhombic structure, with the lattice constants a - 8.09, b = 10.52, c = 3.86 A, andZ = 4. It is probably isotypic with SbSCl and BiSCl, crystallizing in a layer type of lattice (157) (see Section XII,C,5). The selenide halides are monoclinic, with the probable space-group P2,/m. The lattice constants are given in Table XVII. The constancy of the b parameters for all three compounds suggests the general presence of an Al-Se chain extending in that direction (266). 

Figure 3. Relation between the orthorhombic structure types of CrB and UBC (projected along [100]) as well as between the tetragonal structure types of a-MoB and ThBC (projected along [100]). Boron atoms are at the centers of trigonal metal prisms, carbon atoms at the centers of MjB-Oj,. The numbers given indicate the heights in projection.

Thallous halides offer a unique possibility of studying the stereochemistry of the (chemically) inert electron pair, since their structures and their pressure and temperature-dependent phase transitions have been well established. Thallium (1) fluoride under ambient conditions, adopts an orthorhombic structure in the space group Pbcm which can be regarded as a distorted rocksalt structure (Fig. 2.4). In contrast to TIF, the thallium halides with heavier halogens, TlCl, TlBr and Til, adopt the highly symmetric cubic CsCl structure type under ambient conditions [46]. Both TlCl and TlBr, at lower temperatures, undergo phase transitions to the NaCl type of structure [47]. 

Fig. 12.4 (a) Off-[001] perspective view of the a-type orthorhombic structure of R5Tt4. Small and large spheres represent R and Tt, respectively. The p- and y-type structures also have similar atomic arrangements but with different Tt-Tt bonding behavior. 

The lattice parameters a and b become different during the transition from the tetragonal to the orthorhombic structure. Either a > b or a < b results, depending on the direction of the rotation of the octahedra strands. During the phase transition both directions of rotation occur at random domains appear, in which either a > b or a < b. The obtained crystal is a twinned crystal or twin, consisting of intergrown domains. The twin domains are... 

A structure can be tetragonal or not. That is a clear yes-or-no case. When the symmetry of an orthorhombic structure is close to tetragonal, it is nonsense to talk of a tertagonality of the structure. 

FIGURE 4.2 Representation of different carbon types on cobalt, (a) Atomic carbon/ surface carbide in a threefold hollow site, (b) CHX species located in threefold hollow sites, (c) Subsurface carbon lying in octahedral positions below the first layer of cobalt, (d) Cobalt carbide (Co2C) with an orthorhombic structure, (e) Polymeric carbon on a cobalt surface, (f) A sheet of graphene lying on a cobalt surface. The darker spheres represent carbon atoms in all the figures. 

The iron-carbon solid alloy which results from the solidification of iron blastfurnace metal is saturated with carbon at the metal-slag temperature of about 2000 K, which is subsequently refined by the oxidation of carbon to produce steel containing less than 1 wt% carbon, the level depending on the application. The first solid phases to separate from liquid steel at the eutectic temperature, 1408 K, are the (f.c.c) /-phase Austenite together with cementite, Fe3C, which has an orthorhombic structure, and not the thermodynamically stable carbon phase which is to be expected from the equilibrium diagram. Cementite is thermodynamically unstable with respect to decomposition to iron and carbon from room temperature up to 1130 K... 

Fig. 32. Ti distribution per unit cell over the crystallographically different T-sites for the orthorhombic structure (T1-T12, white) and monoclinic (T1-T12, stripes T13-T24, black) structures [Reprinted from Njo et al. (160) with permission. Copyright (1997) American Chemical Society].

Orthopedic devices, 3 721-735 joint replacement, 3 727-735 Orthopedic marrow needles, 3 743-744 Orthophosphate (PO4), in soil, 11 112 Orthophosphates, 18 830-841 20 637 magnesium, 18 839 manufacture of, 18 853-855 Orthophosphate salts, 18 836 Orthophosphoric acid, 18 815, 817-826 condensation of, 18 826 properties of, 18 817-819 solubility of boron halides in, 4 140t orf/zo-phthalic resins, 20 101, 113 formulation of, 20 102 Orthorhombic crystal system, 8 114t Orthorhombic phosphorus pentoxide, 19 49 Orthorhombic structure, of ferroelectric crystals, 11 95, 96 Orthorhombic symmetry, 8 114t Orthosilicate monomers, in silicate glasses, 22 453... 

Structural characteristics. Both natural and synthetic mordenite have an orthorhombic structure that consists of parallel, 12-membered ring channels in the c-direction, having an eliptical cross-section with dimensions of 6,7 x 7.0 A (Figure 9). Smaller 8-membered ring channels with dimensions of 2.9 x 5.7 A, which are perpendicular to the main channels, are too small to allow the movement of molecules from one main channel to another. Mordenite has been synthesized in a "large -port" and "small-port" form that have different sorption properties. A typical unit cell content is Na0[(A10o)o(Si0o)/rJ. 24 HO. 8 28 2 40... 

The crystal structure of these compounds seems to be strongly correlated with the photocatalytic activity [123]. Active materials are characterized by an orthorhombic structure with distorted MOc octahedra, characterized by high dipole... 

A distorted variant of the Ni2In-type structure is the oP12-orthorhombic structure of the Co2Si, (or PbCl2) type which is described in 7.4.3.6. 

Given that the structural transformation of the a-NaFe02-type layered and orthorhombic structures to spinel only requires cation migration, the varying resistance of transition-metal compositions against the transformation (i.e., low resistance for Mn, high for Co) is most likely connected to the diffusion kinetics of the respective 3d transition-metal ions. 

Table 5.33 lists the structural characters of various pure components of pyroxene crystallizing in the stable state, according to the synthesis of Smyth and Bish (1988). Note the doubling of cell edge a in the transition from monoclinic to orthorhombic structure, composition being equal (i.e., clinoenstatite-enstatite clinoferrosilite-ferrosilite). This effect may be represented by the equation... 

The dibasic magnesium phospate trihydrate is a white crystalline powder orthorhombic structure refractive index 1.514 density 2.123 g/cm at 15°C melts at 205°C losing a molecule of water decomposes between 550 to 650°C slightly soluble in water soluble in acid insoluble in ethanol. The heptahy-drate MgHP04 7H20 constitutes white monochnic needles density 1.728 g/cm3 at 15°C sparingly soluble in water (3g/L at 20°C) soluble in acids insoluble in ethanol. 

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