Crystal structure body-centered

The term crystal structure in essence covers all of the descriptive information, such as the crystal system, the space lattice, the symmetry class, the space group and the lattice parameters pertaining to the crystal under reference. Most metals are found to have relatively simple crystal structures body centered cubic (bcc), face centered cubic (fee) and hexagonal close packed (eph) structures. The majority of the metals exhibit one of these three crystal structures at room temperature. However, some metals do exhibit more complex crystal structures. 

The Crystal Structures (Body-Centered and ccp Types) of Tetrakis(hydroxymethyl)methane, C(CH2OH)4... 

With the exception of manganese and urauium, all true metals have one of the following crystal structures body-centered cubic (sodium, potassium, molybdenum), iron face-centered cubic (copper, silver, gold), iron close-packed hexagonal (beryllium, magnesium, zirconium). 

Crystal Structure. Body-centered cubic single-phase p is obtained in the solution treated condition. Close-packed hexagonal o) phase and cph phase a are precipitated dining aging below 400 °C (750 °F) and above 450 C (840 °F), respectively. Omega phase is usually avoided because it causes embrittlement. 

Crystal Structure. Body-centered cubic P phase is obtained after solution treating in the p temperature region and quendiing. Close-padded hexagonal a phase and co phase precipitate dialing aging above and below 425 (795 F), respectively. Compared with Ti-15Mo-5Zr, embrittlement caused by co phase does not occur as predominantly because the amount of q> phase is reduced by the 3% aluminum additions. 

Crystal structure, body centered cubic (bcc) A crystal structure where the basic building block is a cubic unit cell having atoms at each comer and one in the center of the cell. 

Disordered alloys may form when two metals are mixed if both have body-centered cubic structures and if their atomic radii do not differ by much (e.g. K and Rb). The formation of ordered alloys, however, is usually favored at higher temperatures the tendency towards disordered structures increases. Such an arrangement can even be adopted if metals are combined which do not crystallize with body-centered cubic packings themselves, on condition of the appropriate composition. /J-Brass (CuZn) is an example below 300 °C it has a CsCl structure, but between 300 °C and 500 °C a A type transformation takes place resulting in a disordered alloy with a body-centered cubic structure. 

Size effects in the films depend essentially on substrate type. Namely, iron epitaxial film crystallizes into body centered structure on Ag(lOO) substrate independently of film thickness. For the films thicker than five monolayers, Curie temperature Tc coincides with its bulk value Tc = 1,017 K) so that ferromagnetic order appears diiT [Pg.68]

When metalUc radii derived from metals with the same crystal stmcture are plotted against L, the results fall into fom clearly distinguished lines as shown in Figure 2 (the points for Ce, Eu, and Yb are not included as these have different crystal structures, face-centered cubic (Ce and Yb), and body-centered cubic (Eu), while the other metals are hexagonal close packed). ... 

Tao R and Xiao D. 2002. Three-dimensional dielectric photonic crystals of body-centered-tetragonal lattice structure. Applied Physics Letters 80 4702-4704. 

As with other related rare-earth metals, gadolinium is silvery white, has a metallic luster, and is malleable and ductile. At room temperature, gadolinium crystallizes in the hexagonal, close-packed alpha form. Upon heating to 1235oG, alpha gadolinium transforms into the beta form, which has a body-centered cubic structure. 

Fig. 2. Structures for the solid (a) fee Cco, (b) fee MCco, (c) fee M2C60 (d) fee MsCeo, (e) hypothetical bee Ceo, (0 bet M4C60, and two structures for MeCeo (g) bee MeCeo for (M= K, Rb, Cs), and (h) fee MeCeo which is appropriate for M = Na, using the notation of Ref [42]. The notation fee, bee, and bet refer, respectively, to face centered cubic, body centered cubic, and body centered tetragonal structures. The large spheres denote Ceo molecules and the small spheres denote alkali metal ions. For fee M3C60, which has four Ceo molecules per cubic unit cell, the M atoms can either be on octahedral or tetrahedral symmetry sites. Undoped solid Ceo also exhibits the fee crystal structure, but in this case all tetrahedral and octahedral sites are unoccupied. For (g) bcc MeCeo all the M atoms are on distorted tetrahedral sites. For (f) bet M4Ceo, the dopant is also found on distorted tetrahedral sites. For (c) pertaining to small alkali metal ions such as Na, only the tetrahedral sites are occupied. For (h) we see that four Na ions can occupy an octahedral site of this fee lattice.

Stainless and heat-resisting steels containing at least 18% by weight chromium and 8% nickel are in widespread use in industry. The structure of these steels is changed from magnetic body centered cubic or ferritic crystal structure to a nonmagnetic, face-centered cubic or austenitic crystal structure. 

Allotropy in the solid state can also arise because of differences in crystal structure. For example, solid iron has a body-centered cubic structure (recall Figure 9.16, page 246) at room temperature. This changes to a face-centered structure upon heating to 910°C. 

At high pressures, solid II can be converted (slowly) to solid III. Solid III has a body-centered cubic crystal structure. Line bd is the equilibrium line between solid II and solid III, while line be is the melting line for solid III.P A triple point is present between solid II, solid III, and liquid at point b. Two other triple points are present in this system, but they are at too low a pressure to show on the phase diagram. One involves solid II, liquid, and vapor while the other has solid I, solid II, and vapor in equilibrium. 

Crystal structure cubic, body-centered Density (g/cm ) 7.20 Melting point (°C) 1865... 

The most important metals for catalysis are those of the groups VIII and I-B of the periodic system. Three crystal structures are important, face-centered cubic (fee Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au), hexagonally dose-packed (hep Co, Ru, Os) and body-centered cubic (bcc Fe). Figure 5.1 shows the unit cell for each of these structures. Note that the unit cells contain 4, 2, and 6 atoms for the fee, bcc, and hep structure, respectively. Many other structures, however, exist when considering more complex materials such as oxides, sulfides etc, which we shall not treat here. Before discussing the surfaces that the metals expose, we mention a few general properties. 

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