Crystalline system Triclinic

Primitive three-dimensional lattices have been classified into seven crystalline systems triclinic, monoclinic, orthorombic, tetragonal, cubic, trigonal, and hexagonal. They are different in the relative lengths of the basis vectors as well as in the angles they form. An additional seven nonprimitive lattices, belonging to the same crystalline systems, are added to the seven primitive lattices, which thus completes the set of all conceivable lattices in ordinary space. These 14 different types of lattices are known as Bravais lattices (Figure 3). 

This notation defines the symmetries of a crystalline material in terms of point, plane, and space groups and is closely tied to the crystal systems (triclinic, monoclinic, tetragonal, etc.) and crystal class. It is also related to Schoenflies and orbifold notations and offers a definition of the relevant symmetry axes. 

These general results correspond to the case of unit cell of triclinic syngony. The complete list of the results for the seven crystalline systems of Table 2.2 is presented in Table 3.3 (Putz, 2006). 

Iodine is a bluish black, crystalline soHd having a metallic luster. It is obtained in shiny flakes or prills that can be easily cmshed to powder. Iodine crystallines in rhomboidal plates belonging to the triclinic system. 

We have been more concerned with the nature of the water around proteins and peptides. To this end we have investigated the structure and energetics of the solvent, both ordered and disordered around the enzyme lysozyme, in the triclinic crystal[l7d]. In addition to lysozyme, we have characterized the water structure and fluctuations in the crystal of a cyclic hexapeptide, (L-Ala-L-Pro-D-Phe)9[20]. and studied the effect of solvent on the conformation of the dipeptide of alanine[2l] and on the equilibria between extended and helical alanine polypeptides such as those discussed in the previous section[22]. The latter systems simulate aqueous solution conditions rather than crystalline environment. 

Despite the fact that the triclinic system is the only crystallographic system that unequivocally allows singlecrystal orientations to provide both enhanced in-plane and out-of-plane NRVS spectra, many other crystalline heme derivatives fortunately have all porphyrin planes close to being parallel to a common crystallographic plane. For example, [Fe(TPP)(l-MeIm)(NO)] has four independent porphyrin plane orientations, but all planes are within 13.8° of a common plane in the crystal. Data were collected using this common plane as the crystal-orienting plane to obtain an in-plane and an out-of-plane spectrum. As shown in Figure 10, a comparison of the in-plane , out-of-plane , and powder spectra show that useful intensity enhancements are still evident. Moreover, and fortunately, this situation of nearly coincident planes appears to be moderately frequently observed. 

Dark orange in colour, potassium diehromate exists in two crystalline forms, the stable form belonging, apparently, to the asymmetric class of the triclinic system ... 

All these results apply to a completely general triclinic crystal system whose elastic properties are expressed by the twenty-one independent quantities Cy or Jy. For crystals of higher symmetry there are further relations between the Cy or 5y which reduce their number still further. For the hexagonal and cubic systems these relations are illustrated in fig. 8.1, together with similar relations for a completely isotropic, non-crystalline material. It can be seen that for a hexagonal crystal like ice there are only five non-zero independent elastic constants Jn, i3> % and 44 or the corresponding Cy. 

Crystalline kris-ta-bn [ME cristallin, ft. MF L MF, fr. L crystallines, fr. Gk krys-tallinos, fr. krystallos] (15c) adj. A substance (usually solid but can be liquid) in which the atoms or molecules are arranged in a definite pattern that is repeated regularly in three dimensions. Crystals tend to develop forms bounded by definitely oriented plane surfaces that are harmonious with their internal structure. They may belong to any of six crystal systems cubic, hexagonal, tetragonal, orthorhombic, monoclinic, or triclinic. 

Fig. 1. Orientation of crystalline magnetic tensors in Fig. 2. Orientation of crystalline magnetic tensors in triclinic system. monoclinic system.

There are seven possible space lattices which entirely describe both inorganic and organic crystalline materials. These are called the seven crystal systems (i.e., cubic, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, and triclinic). 

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