Herringbone pattern

Figure 10.9 STM images showing structural changes induced by sulfur adsorption. (a) Clean Au(lll) surface showing very regular herringbone pattern, (b) Close-up of the disordered herringbone pattern at low coverage of sulfur (<0.1ML). (c) Atomically resolved images of the Au atoms underlying approximately 0.3 ML sulfur adsorbed Au(lll). (Reproduced from Ref. 34).

The geometries of the open (HF) clusters in Figs. 5.23(a)-(c) were chosen to mimic (and extend) the bent structure of the dimer in the manner that might be expected from a simple dipole-dipole picture. In these species the angle was constrained to be the same for each monomer, thus creating a zig-zag onedimensional chain of an extended herringbone pattern (but with 0hf - f and all other... 

Detailed fracture and metal failure analysis is usually a very reliable and extensive aspect of investigations of major loss incidents. For most small to medium investigations, macroscopic evaluation is typically sufficient. Macro evidence, such as indications of shear or brittle failure on fracture faces, lines showing detonation direction, and the chevron (herringbone) pattern all provide valuable clues to sequence, type, and cause of the failure.(See Figure 8-9.)... 

The elbow in the herringbone pattern and the U connections are ways to relieve the surface strain created by the 22 X reconstructions. Near the elbow and the U connection, the atomic arrangement is different from the uniaxial regions. Models have been proposed based on energetics considerations (Barth et al., 1990 Chambliss ct al., 1991a). In the high-resolution... 

See Atomic units Helical springs 247, 373—374 allowable stres.s 374 materials 247 stiffness 247, 374 working stress 374 Herringbone pattern 329 Hertz formulas... 

Fig, 4G0 others ars ornamented with incised lines and herringbone patterns, or with clusters of small studs and it is also common to find them having their sides depressed in compartments, after the manner shewn in Fig. 461. 

FIGURE 6 Two types of gasketed plates for the gasketed-plate heat exchanger (a) parallel-corrugated plate (b) cross-corrugated plate ( herringbone pattern or chevron ). 

This conformational mobility is exemplified in the structures of Ni(oep) (Fig. 26). In the triclinic form of Ni(oep)194-1 the molecules are planar and centrosymmetric (Fig. 26 a) and are stacked inclined relative to the stacking axis in a herringbone pattern similar to that adopted by most of the metallophthalocyanines. By change of solvent, Ni(oep) can be made to crystallize in a tetragonal form195) in which the molecule has crystallographi-... 

For unsubstituted HBC, an X-ray single-crystal study164 showed that the molecules pack in the so-called herringbone pattern, which optimizes the ji—ji interactions between adjacent disks. In ref 22, it was hypothesized that HBC—C12 adopts the same colum-... 

Figure 24. A representation of the proposed stacking of the aromatic cores in HBC—C12, based on the structure of unsubstituted HBC, which is known, from a X-ray singlecrystal study,164 to crystallize in the so-called herringbone pattern. Three HBC—Ci2 molecules are shown the molecules above and below the central HBC—C12 molecule are indicated by dashed and dotted lines, respectively. (Reproduced with permission from ref 22. Copyright 1999 American Chemical Society.)...

In contrast to self-assembly or self-organization, which rely on the intrinsic properties of a system, template-assisted assembly provides a way to externally control the formation of a structure. The template contains spatial information, which is expUcitly imposed on the building blocks of a system. In a first step this can be a mild template effect, which only assists in the pattern formation. This effect is encountered, for example, in the structure formation of PTCDA on Ag(l 11) and Ag(l 10) [8]. In these cases the final structure of the overlayer is not only controlled by the mutual interaction of the PTCDA building blocks (self-assembly) but also assisted by the substrate. The different crystallographic orientation of the respective surfaces leads to the formation of either a herringbone pattern or a Hnear assembly on Ag(l 11) and Ag(l 10), respectively (Fig. 2). Similar results have been found for PTCDA on Cu(l 11) [9] and Cu(l 10) [10] as well as Au(l 11) and Au(lOO) [llj. 

Fig. 2.8 Costal structure of the radical-ion salt tetracyano-quinodimethane (TCNQ) Tetra-thiofulvalen (TTF). The crystal is monoclinic. The donors (TTF) and the acceptors (TCNQ) are arranged in separate stacks which are parallel and alternate along the a direction. These form a herringbone pattern. The molecular planes are inclined relative to the stack axes at an angle of 24.5° (TTF) or -34°...

Fig. 2.10 The ct7stal structure of naphthalene, anthracene, tetracene, and pentacene. These aromatic compounds crystallise in the herringbone pattern. Their crystal-structure data are given in the first part of Table 2.3, and the orientation of the individual molecules in these crystals are indicated in the lower part of the Table.

Some aromatic hydrocarbons, for example pyrene and perylene, also crystallise in a herringbone pattern however, the structural units of these lattices are pairs of molecules which form sandwich-like dimers (see Figs. 2.12 and 2.13 as well as Table 2.4). The two partners are bound together only weakly and absorb light like monomers, but they flouresce as dimers. This interesting phenomenon is called excimer emission (excimer stands for excited dimer ) more will be said about this topic later in Chap. 5. By the way, perylene (see also Table 2.4) crystallises not only in the dimer-like a phase but also in a jS phase (Fig. 2.13). In the latter, which... 

---