Crystals origin

Figure 3.23. A growth spiral on a silicon carbide crystal, originating from the point of emergence of a screw dislocation (courtesy Prof, S, Amelinckx).

Reduction of (4-CH3—C6H4)3PAuN03 by NaBR, in ethanol (molar ratio 4 1) yields a red solution from which a tetraphenylborate salt of the cation [(4-CH3—CgHihPAulg 2 can be precipitated in the form of yellow crystals as a small by-product. [The main product appears in the form of red crystals, originally not further specified (10,12).] The X-ray diffraction analysis gave the cation structure shown in Fig. 4. 

Ozima, M., Tatsumoto, M. (1997) Radiation-induced diamond crystallization Origin of carbonados and its implications on meteorite nano-diamonds. Geochim. Cosmochim. Acta, 61, 369-76. 

Broadening of electronic states in molecular crystals originates either from relaxation to other states of lower energy (at very low temperatures) or from the presence of a continuum of various configurations, connected with the presence of disorder. We consider here the broadening in the absence of disorder, the so-called intrinsic or homogeneous broadening. Disorder is examined in Section IV. 

The morphological symmetry differences between the acetanilide and p-chloroacetanilide crystals originate from their internal structures. The acetanilide molecules appear in pairs and the two molecules in each pair are related by an inversion center. On the other hand, the p-chloroacetanilide molecules are all aligned in one direction. The molecular arrangements in the two crystals are shown in Figure 2-33. 

With Mo(CO)g, 1,3-cyclohexadiene produces at 100°C a low yield of yellow diamagnetic crystals, originally reported (220) as the first metal 7T complex having two diene ligands (12). Its proton NMR spectrum corresponds, however, to (C8Ho)(CgH7)Mo(CO)2 (13) (229). The true... 

Chloro-l-naphthol. The reagent should be discarded when crystals, originally white, turn to grey. It is stable for a few months at-20°C when stored desiccated. It can also be stored as a solution in ethanol at-20 C. 

Other equally remarkable optical properties are associated with the selective reflection. At normal incidence, the reflected light is circularly polarized one circular component is totally reflected, while the other passes through unchanged. Also, quite contrary to what is found in normal substances, the reflected wave has the same sense of circular polarization as that of the incident wave. This is an important difference between the nature of the optical rotation of normal substances and of cholesteric liquid crystals. While the more familiar cases of optical rotation have their origin in the selective absorption of one circularly polarized component of the light, the form optical rotation of the twisted structure in cholesteric liquid crystals originates in the selective reflection of one circularly polarized component of the light. 

W. Wijaranakula, Characterization of crystal originated defects in czochralski silicon using nonagi-tated Secco etching, J. Electrochem. Soc. 141, 3273, 1994. 

Fig. 3.1.3. Amygdaloid from Malpelo Island, D.F., Colombia. Some of the amygdules and some of the lathlike crystals of the mesostasis are phosphates of aluminium, whereas other amygdules are opal (or mixtures) and some of the lathlike crystals (originally feldspars) are now quartz. Magnification 33x. Reproduced with permission (McConnell, 1943).

Lahav, M., Weissbuch, I., Shavit, E., Reiner, C., Nicholson, G.J., Schurig, V. Parity violating energetic difference and enantiomorphous crystals - caveats reinvestigation of tyrosine crystallization, Origins of Life and Evolution of the Biosphere. (2006) 36, I5I-I70. 

Even at the liquid-helium temperature the hfs of the most of excited crystal-field sublevels is masked by the spontaneous relaxation broadening. Strong electron-phonon interaction effects in CsCdBr3 Ln crystals originate from the specific density of phonon states that has large maxima in the low-frequency region (20-40 cm ) in the perfect crystal lattice (see Fig. 4 and Ref. 

Special models have been developed for the crystallization of these and related stiff-chain aromatic copolymersThe basic crystal was suggested to be of the condis crystal type with rotational disorder based on conformational mobility, proven by mechanical and dielectric relaxation The morphology of the superimposed crystals was proposed to be based on a matching of order between adjacent molecules similar to cold crystallization originally proposed for the crystallization of PET-copolymers from the glassy state... 

The morphological symmetry differences between the acetanilide and / -chloroacetanilide crystals originate from their internal structures. The acet-... 

The selective adsorption of enantiomers of transition metal complexes on quartz proved to be more successful. For the first time, in 1935, Tsuchida and colleagues reported the partial resolution of several racemic Cr- and Co-complexes using chromatographic adsorption on columns composed of d-or /-quartz crystals originating from Kimbusen and Naegi deposits. The steric... 

Figure 2. Phase from ammonium oleate (left), Lehmann s [14] first seemingly living crystals (original photograph as a kind gift of Hans Kelker) [13], and life s informational component s liquid crystalline DNA texture [15] (right), the present realization of Lehmann s early visions.

---