Crystal structure Relationships

Rozier, P. and J. Galy. 1997. Ag, 2V308 crystal structure Relationship with Ag2V4On y and interpretation of physical properties. J. Solid State Chem. 134 294—301. 

Rozier P, Galy J (1997) Agi 2V3O8 crystal structure Relationship with Ag2V40n y interpretation of physical properties. J Solid State Chem 134(2) 294—301... 

An example of research in the micromechanics of shock compression of solids is the study of rate-dependent plasticity and its relationship to crystal structure, crystal orientation, and the fundamental unit of plasticity, the dislocation. The majority of data on high-rate plastic flow in shock-compressed solids is in the form of ... 

Epitaxy. There is often a sharp orientation relationship between a singlecrystal substrate and a thin-film deposit, depending on the crystal structures and lattice parameters of the two substances. When such a relationship exists, the deposit is said to be in epitaxy with the substrate. The simplest relationship is parallel orientation, and this is common in semiconductor heterostructures, but more complex relationships are often encountered. 

MW and MWD are very significant parameters in determining the end use performance of polymers. However, difficulty arises in ascertaining the structural properties relationship, especially for the crystalline polymers, due to the interdependent variables, i.e., crystallinity, orientation, crystal structure, processing conditions, etc., which are influenced by MW and MWD of the material. The presence of chain branches and their distribution in PE cause further complications in establishing this correlation. 

Although it is important that no water should exist in the cathode materials of nonaqueous batteries, the presence of a little water is unavoidable when Mn02 is used as the active material. It is believed that this water is bound in the crystal structure, and that it has no effect on the storage characteristics, as shown in Fig. 27, where the relationship of the MnO,... 

Sn2Sl2, was said (385) to exist in an a and a )8 form. The crystal structures of both forms have been elucidated (119, 239, 240, 388). Apart from questions that still remain concerning the true relationship of a-and )8-Sn2Sl2, a publication by Fenner (121) on the synthesis and structure of a new ternary phase, Sn4SIe, contradicts both of the phase diagrams already mentioned. 

Figure 1. Relationship among the crystal structures of Re3B and Mo2lrB2. Full circles are atoms in 1/2 open circles are atoms in 0 the two metal sites in Re3B (8f and 4b) are differentiated by larger and smaller circles smallest circles are B atoms. The structure of Mo2lrB2 is generated by a shift of every second prism row of Rc3B (vector c/4).

Fig. 4.6 Crystal structure of Prl2-V. (a) The cubic face-centered unit cell, (b) One cluster Pr4 l4l,2. (c) Hexagonal setting of the structure exhibiting the close relationship to the CdCl2-type of structure.

Lewis DF, Lake BG, Bird MG. Molecular modelling of human microsomal epoxide hydrolase (EH) by homology with a fungal (Aspergillus niger) EH crystal structure of 1.8 A resolution structure-activity relationships in epoxides inhibiting EH activity. Toxicol In Vitro 2005 19 517-22. 

Aside from the conventions mentioned for the cell choice, further rules have been developed to achieve standardized descriptions of crystal structures [36], They should be followed to assure a systematic and comparable documentation of the data and to facilitate the inclusion in databases. However, contraventions of the standards are rather frequent, not only from negligence or ignorance of the rules, but often for compelling reasons, for example when the relationships between different structures are to be pointed out. 

G. C. Chapuis, Symmetry relationships between crystal structures and their practical applications. In Modem Perspectives in Inorganic Crystal Chemistry (E. Parthe, ed.), p. 1. Kluwer, 1992. 

In order to understand the relationship between the properties of a material and its structure, which is the raison d etre of the materials scientist, three important experimental areas of investigation may be necessary. Firstly, of course, the physical or mechanical properties in question must be measured with maximum precision, then the structure of the material must be characterised (this itself may refer to the atomic arrangement or crystal structure, the microstructure, which refers to the size and arrangement of the crystals, or the molecular structure). Finally, the chemical composition of the material may need to be known. 

These results illustrate that electrochemical techniques can be employed to synthesize a vast range of [Si(Pc)0]n-based molecular metals/conductive polymers with wide tunability in optical, magnetic, and electrical properties. Moreover, the structurally well-defined and well-ordered character of the polymer crystal structure offers the opportunity to explore structure/electro-chemical/collective properties and relationships to a depth not possible for most other conductive polymer systems. On a practical note, the present study helps to define those parameters crucial to the fabrication, from cheap, robust phthalocyanines, of efficient energy storage devices. 

With reference to hosts and a guest, molecular assemblies have to conform to certain circumstances, generally called complementary relationships. They involve both steric and electronic terms. The objects may be achieved by the use of properly chosen sensor groups and by a suitably tailored basic skeleton as exemplified by the present scissor- or roof-shaped host molecules. From the point of view of the introductory thoughts of this chapter (cf. Sect. 3.1), it is a matter of consideration to see how consistent the scissor or the roof simile is in the light of crystal structures. 

Among various superconductors, compounds with the A15 (Cr3Si) crystal structure have the highest critical temperatures. This crystal structure has a simple relationship with the Ll2 structure (Ito and Fujiwara, 1994) as illustrated in Figure 8.9. When the unit cells are aggregated, the face-centered pairs of atoms form uniform chains of transition metal atoms along three orthogonal directions. This feature may be related to the relatively stable superconductivity in compounds with this structure. 

Figure 8.9 Relationship between the Ll2 (Ni3Al) and the A15 (Cr3Si) crystal structures. In both cases the cube corners are occupied by the non-transition elements (A1 and Si), but the face-centers are occupied differently by one transition metal atom in the Ll2 case, and by a pair of transition metal atoms in the A15 case. An additional difference is that the cube center is unoccupied in Ni3Al, but is occupied by a Cr atom in Cr3Si.

---