Centering crystal structure

The Body-Centered Crystal Structure of Bis(salicylaldehydato) copper(II)... 

The 3-2PTOT Body-Centered Crystal Structures of p-Brass, CuZn... 

Figure 11.5. The face-centered crystal structure of orthorhombic oxalic acid. On the left is the cell projected along the a0 axis. Only one molecule at a corner and three molecules in the centers of the faces are shown for clarity. On the right, a packing drawing shows all molecules in the cell with the same view.

The 3 2PTOT(t) Body-Centered Crystal Structure of C(SCH3)4... 

Hydrocyanation of styrene 26 (eq. (7)) has been examined in some detail. With Ni[P(0-o-tolyl)3]4 27 the branched nitrile 29 is strongly favored over the linear one, which is explained by the intermediary formation of a detectable alkyl species 28. The stability of this intermediate is attributed to the donation of aromatic ring electrons to the coordinatively unsaturated metal center. Crystal structures of related compounds are reported in the literature [53, 54]. 

All prefactors in Eq. 2.107 (i.e. g, t,f, Af, and Af") are identical for the pairs of the symmetrically equivalent atoms. Hence, Bragg reflections in which the sums of all Miller indices are odd should have zero structure amplitude and zero intensity in any body-centered crystal structure. In other words, they become extinct or absent, and therefore, could not be observed and are forbidden. 

Our language is rather casual here. The crystal structure of copper is of the cubic dose-packed (cep) type and, because there is only one type of atom, this is ecprivalent to the face-centered cubic (fee) structure for this special case. Although not every F-centered crystal structure belonging to the cubic system (e.g.. Si or NaQ) can be considered dosely packed, the simplified notion cep = fee is so ubiquitous in the literature that we also use it in this book. 

The metal itself has a body-centered crystal structure. 

Cubic close-packed (face-centered) crystal structure... 

The nucleophile in p-lactam hydrolysis by biomimetic Zn(II) complexes has been reported previously to be either a bridging hydroxide or a terminal water molecule. A bridging hydroxide was ruled out as nucleophile [26]. It is unlikely that this is the nucleophile in the reported complex as the two Cd(II) ions are separated by 4.162 A and thus too far away to establish a single hydroxide bridge between the two metal centers. Crystal structures with pyrazolate based ligands reported by Meyer et al. support this proposal [47, 48]. There are a number of findings that led to the proposal that the metal bound alcohol is the nucleophile (Fig. 5.22) ... 

The body-centered crystal structures of carbon and low-alloy steels are susceptible to four types of hydrogen damage, two of which are low-temperature processes and two are high-temperature processes ... 

For the face-centered crystal structure, the centers of the third plane are situated over the C sites of the first plane (Figure 3.18a). This yields an ABCABCABC. . . stacking sequence that is, the atomic alignment repeats every third plane. It is more difficult to correlate the stacking of close-packed planes to the FCC unit cell. However, this relationship is demonstrated in Figure 3.186. These planes are of the (111) type an FCC unit cell is outlined on the upper left-hand front face of Figure 3.186 to provide perspective. The significance of these FCC and HCP close-packed planes will become apparent in Chapter 7. 

While the 20 Group 1 metal halides all adopt either a face-centered or a body-centered crystal structure, crystals of the 32 dihalides of the Group 2 and 12 metals form a bewildering array of at least 15 different structure types. Both the crystal and the gas-phase structures have recently been described and correlated in comprehensive reviews by Hoffman and coworkers [16, 17]. In this section we shall be particularly concerned with the crystal stractures of the eight metal difluorides and the four mercury dihalides. 

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