Rhombus

Fig. XVII-18. Contours of constant adsorption energy for a krypton atom over the basal plane of graphite. The carbon atoms are at the centers of the dotted triangular regions. The rhombuses show the unit cells for the graphite lattice and for the commensurate adatom lattice. (From Ref. 8. Reprinted with permission from American Chemical Society, copyright 1993.)...

Rhombus (equilateral parallelogram) A = V2ah where a, h are the lengths of the diagonals. 

Rauten-flach, n., -flachner, m. rhombohedron. -flache, /. rhombus. 

By means of the rhombus rules, if values are given for the elements occurring along the broken line at the top, then all other elements can be computed. The numbers to be taken are... 

Resonance, nonlinear, 354 Resonance, subharmonic, 372,376 Rhombus rules, 85 Risk matrix, 315 Risk rule, 315... 

Triphosphorus anion Pj" (16e) was calculated to be linear [11]. Honea et al. [12] prepared and isolated Si (16e) by low-energy deposition into a solid nitrogen matrix, and carried out a Raman spectra study to show that Si is a planar rhombus The Al " tetraanion (16e) stabilized by the three LP ions in the most stable structure of LijAl " is rectangular in a capped octahedral arrangement [13],... 

The global minimum of a neutral Li molecule with AN valence electrons N= 1) does not adopt a square structure (D ) but a rhombus structure (D ) [43]. The Raman spectroscopy supported the rhombic structure for the Li [44], Na and clusters [45,46]. 

Upon substituting the sum + J// for 2 jy/ in the right-hand side of equation (60) the resulting three-layer rhombus scheme known as the Du-Fort—Frankel scheme... 

Substitution of the last expression into (61) yields (62). As a matter of fact, the rhombus scheme is some modification of the Richardson scheme with the extra member on the left-hand side of (61) h " which assures... 

From such reasoning it seems clear that the rhombus scheme provides the conditional approximation... 

A particular case of scheme (79) is the Du Fort-Frankel scheme known as the rhombus scheme for the heat conduction equation... 

Fig. 4.12 (a) CdSe wurtzite unit cell (b) schematic illustration of a hexagonal (wurtzite) CdSe basal plane on a (111) section of the gold lattice, emphasizing the 2 3 lattice match. Note the [111] Au//(0001)CdSe orientation, with the CdSe a-directions aligned along the (llO)Au. The outlined rhombus indicates the projection of a CdSe unit cell. (Adapted from [112])... 

A hysteresis cycle in the molar susceptibility measurements has been observed for [Ni2(Medpt)2(N3)2(/r-N3)2] (883). This has been ascribed to a phase transition caused by an asymmetrization process of the rhombus-like centrosymmetric [Ni-(N3)2-Ni] core that occurs with falling temperature. The asymmetrization transition can be explained in terms of a second-order Jahn-Teller distortion, taking into account the local symmetry of the dinuclear [Ni-(N3)2-Ni] entity (D2h, rhombic symmetry) before the arrangement.2128... 

Finally, a highly complex structure is created when /ra s-Cd(4-ampy)2 (4-ampy = 4-aminopyri-dine) and Cd(4-ampy)(ame) Ag(CN)2 units (ame = 2-aminoethanol) are linked by bridging //- Ag(CN)2 groups to form a 2-D network with rhombus meshes and almost linear chains. These antiparallel chains in pairs embrace the nets.221... 

Fig. 1. Location of various high-symmetry sites in the diamond structure. T is the tetrahedral interstitial site, H is the hexagonal interstitial site, B the bond center, and C is at the center of a rhombus formed by three adjacent Si and the nearest T. The M site is midway between two C sites it is also located midway between B and a neighboring H site.

Fig. 11 (Top) Perspective view of an [Fe]4 rhombus in the [Fe(bpe)2(NCS)2]-CH3OH 2D polymer. (Bottom) Schematic representation of the interpenetration of a layer lying in the plane of the sheet and three orthogonal layers (left). Perspective view of the crossing of two independent net systems defining the rectangular channels (right). Balls and sticks represent iron atoms and bpe ligands, respectively...

Solv=MeOH, EtOH and PrOH), and l,4-bis(4-pyridyl-butadiyne) (bpb, n= 0.5, Solv=MeOH). Like the btr derivative, compressed [FeN6] pseudo-octahedral sites define the knots of the square- or rhombus-shaped windows, which constitute the layered grid structure of the three compounds. Stacking of these layers in the crystal defines their most important structural differences, which are determined by the ligand size and crystal packing efficiency. In principle, the 2D grids are organised in a fashion similar to that described for the [Fe(btr)2(NCX)2]-H20 system the parallel layers are alternated so that the iron atoms of one layer lie vertically above and below the centres of the squares formed by the iron atoms of the adjacent layers. 

The equatorial positions of the octahedron are occupied by the CN moieties of the [Ag(CN)2] groups. As in the pz derivative, each [Ag(CN)2] group connects two iron atoms defining the edges of a Fe4[Ag(CN)2]4 rhombus. However, the edge-shared rhombuses define 2D corrugated nets in contrast to the pz derivative, due to the three-coordination of the Ag atoms (see Fig. 19). A schematic view of one 3D network is depicted in Fig. 20. 

Figure 4. STM picture of the rhombus type PAH 38. Picture taken from ref. [20],...

Particular organic ligands such as acetylenes and allenes can induce opening of the tetrahedron to give a folded rhombus, which is usually classified as a butterfly structure (Fig. 17). This butterfly structure is also rather surprisingly found for the anion [Fe4(CO)13H] 178, as shown in Fig. 18. 

A rhombus is a parallelogram with four congruent sides. Refer to figure I, above. 

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