Crystal structures projections

Figure 4. Possible unit cells of the PBT crystal structure (projection down the axis)...

Figure 5.7 X-ray crystal structure projections of copper-catecholate adducts obtained by Comba and co-workers [41] (a, c and d), and x-ray crystal structure of one of the dicopper(ll)-catecholate adducts crystallized by Meyer and coworkers (b) [42],...

Figure 3 (a) Aragonite. The crystal structure projected down the c-axis (Gaines et aL, 1997, p. 441). (b) Plot of the... 

Figure 5 (a) Fluorapatite. The crystal structure projected down the unique c-axis showing the hexagonal disposition of the Ca ions and PO4 groups around the F ion. Caj in sevenfold coordination, C 2 in ninefold coordination (Gaines et al., 1997, p. 855). (b) Plot of the best fit, 15%, and next best fit, 30%, of cations that could take the place of Ca in sevenfold ( ) and in ninefold ( ) coordination in fluorapatite structure (source Skinner et al., 2003). 

F. 21. Arrangements of the structural units (Fig. 19) of tellurium and telluriiun suhhalides in the conesponding crystal structures. Projections along the macromolecular structmal units a-Tel is projected along c ... 

Fig. 54. Barrerite. Crystal structure projected along b axis water molecules are omitted for clarity [99S1].

Fig. 28. Mazzite-Na, mazzite-Mg. Crystal structure projected along c (a) mazzite-Na and (b) mazzite-Mg. The larger, darker spheres represent extra-framework cations and the smaller, lighter spheres H2O molecules. The thin lines represent bonds between extra-framework cations and framework oxygen atoms with interatomic distances less than 3.2 A. The double lines represent bonds between Na cations and H2O molecules with interatomic distances less than 3.2 A. Thick black lines are bonds between H2O molecules and framework oxygen atoms with interatomic distances less than 3.0 A. (c) The coordination of Nat (cl) and Nall (c2) showing the anisotropic thermal ellipsoids of Na and framework oxygens. In (cl), W2 and W2A and in (c2) W1 and W8 are alternately present in the bonding to Na atoms [05A1].

The iron carbide cementite is an important component of steel. The crystals are orthorhomhic with a = 4.524, b = 5.089, c = 6.743 A. The crystal structure projected along b is shown on the right, in which iron atoms are represented hy larger circles and the origin is at the lower right corner. 

Fig. 3. Crystal structure of the compound C o(S8)2CS2 projected normal to the a-axis. Large cireles denote Coo, small eireles denote sulfur, black balls denote carbon. In this structure, the Coo-Ceo distanee is nearly 11 A, and the diameter of the Ceo molecule has been reduced relative to the other atoms for clarity [54].

Figure 10.2 Crystal structure of GeF2 (a) projection along the chains, and (b) environment of Ge (pseudo trigonal bipyramidal). The bond to the unshared F is appreciably shorter (179 pm) than those in the chain and there is a weaker interaction (257 pm) linking the chains into a 3D structure.

Fig. 5. The projection of crystal structure of 97 (IQ) along the c-axis (hydrogen bonds are shown with heavy broken lines).

Fig. 31 Crystal structure of Rb sNb30Ft8. Projection on the plane (001). Numbers in brackets are the atom coordinates on the z-axis in percents of c parameter. Structure of NbOFj chains and NbFf polyhedron. Reproduced from [209], A. I. Agulyansky, V. E. Zavodnik, V. Y. Kuznetzov et al. Neorgan. Mater. 27 (1991) 380, Copyright 1991, with permission of Nauka (Russian Academy of Sciences) publishing.

Figure 7. Crystal structures of (a) hollandite, (b) romanechite (psilomelane), and (c) todorokite. The structures arc shown as three-dimensional arrangements of the MnO() octahedra (the tunnel-tilling cations and water molecules, respectively, are not shown in these plots) and as projections along the short axis. Small, medium, and large circles represenl the manganese atoms, oxygen atoms, and the foreign cations or water molecules, respectively. Open circles, height z. = 0 fdled circles, height z = Vi.

Figure 16. Crystal structure of a-MnOOH. The structure is shown as a three-dimensional arrangement of the Mn(0,0H)6 octahedra with the protons filling the [2 x 1] tunnels, and as a projection along the short crystallographic oaxis. Small circles, manganese atoms large circles, oxygen atoms open circles, height z - 0 filled circles, height z = A The shaded circles represent the hydrogen ions.

Although a number of solid compounds of plutonium were synthesized by ultramicrochemical techniques during our first year and a half at the Metallurgical Laboratory, it was not until November, 1943 that a positive identification of a crystal structure was made. W. H. Zachariasen joined the project in the fall of 1943 and very soon began to make definitive identifi-... 

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

Figure 4. Projection of the crystal structure of Ti3P along [001] and relation to the structure type of NdCo4B4 (broken line).

Figure 1. The crystal structure of ThB4-type tetraborides. (a) The covalent boron skeleton, (b) Atomic arrangement in MB4 (projected along 5).

Fig. 12 The crystal structure of 1,4-DCB projected on to the (100) plane. (From Hasegawa era/., 1985, with permission.)...

In many respects the fragment approach is ideally suited to projects which have X-ray crystal structures available. The fragments are small and relatively weak binders, but they often only possess one pharmacophoric element that binds to a specific feature on the target. If this interaction is identified by X-ray structure determination, then project teams can propose specific plans which maintain that critical interaction, and ideally optimize binding through other vectors in their fragments. 

Fig 1. Stereographic projection of the crystal structure of the 2 1 inclusion compound between CS2 and cavitand 1. One CS2 ( guest ) molecule is encapsulated within the host cavity, the second CS2 ( solvent ) being located between the complexed entities (taken from Ref.27>)... 

Fig. 6. Projection of a portion of the disordered thieno-[3,4-d] thiepin (13, X=S) crystal structure viewed along the c axis...

Design, synthesis and structure determination of molecules, the skeletons of which are distorted by steric congestion and/or by charge perturbation, therefore, has become an additional research project of the Frankfurt group since 1989 [2,3]. Of the altogether about 100 single crystal structures determined in the meantime, about a dozen are of silicon organic compounds [5] (cf. examples in Fig. 1). 

Fig. 7 Projection of the crystal structure of [Fe(btr)3](C104)2 on the (ab) plane. The hydrogen atoms and the perchlorate anions are omitted for clarity...

Figure 1.14 Crystal structure of sodium chloride, NaCl (a) a perspective view of one unit cell and (h) projection down [010], the b axis.

Fig. 6. Structural model of the SSZ-48 crystal structure, showing the projected positions of the organic template within the pores, of SSZ-48 (5).

---