Crystalline disorder

Among crystalline solids, typical second-order transitions are associated with abrupt intermolecular conformational, rotational, and vibrational changes and/or with abrupt changes in crystalline disorder and/or defects [7], These changes in crystalline solids are sometimes difficult to assign without the use of appropriate spectroscopic techniques such as solid-state NMR or a diffraction procedure such as single-crystal X-ray diffraction. 

The most common definition of a microemulsion characterises it as a thermodynamically stable, transparent, optically isotropic, freely flowing surfactant mixture, often containing co-surfactants (e.g. alcohol) and added salts [37]. We restrict the definition further to non-crystalline (disordered) aggregates, since crystalline isotropic phases are better considered as liquid crystalline mesophases. Indeed, the most succinct description of a microemulsion would involve its microstructure. However, this has proven to be a very equivocal issue. So much so that until very recently it was widely believed that microemulsions were devoid of microstructure hence the thermod)mamic definition. 

The Hedvall effect [77] ascribes enhanced reactivity within particular temperature intervals in reactions of solids as being due to increased ionic mobility during a condition of crystalline disorder or recrystallization. Gam and Habash [78] selected the reaction ... 

RMCprolile Reverse Monte Carlo modelling of crystalline disorder, D. A. 

These values fluctuate within zblOcm depending on variations in oxygen stoichiometry and crystalline disorder. The results of normal coordinate analysis [154] indicate considerable mixing among the vibrations represented by the Cartesian coordinates of individual atoms. 

Second, and even more important, this sintering is accompanied by crystalline modifications (Figure 1). The transformation of an aluminum hydroxide to corundum through transition aluminas causes a crystalline disorder, the amplitude of which depends on the specific structural sequence. Some of the aluminas consist of mixtures that undergo parallel... 

The crystalline disorder is due to the presence of the two possible (cis) and (trans) conformers (Figure 6.6). The enantiopure compounds (P)-(TTF-oxa)2AsF6 (P)-(6.13) and (5)-(TTF-oxa)2AsF6 (5)-(6.13) crystallize in the P-1 space group with one anion and two independent donor molecules with a (cis) and (trans) conformation. Overall, the stracture of the enantiopure compounds is less disordered, even if the structure of the ft type is fairly close to the racemic compound, with a head-to-tail arrangement of the cations. 

Figure 33 Difference spectra (spectrum after irradiation minus spectrum prior to irradiation for 15 min) for the N-and N-labeled compounds (A) (OEP)Ru(NO)(0-/-C5HTq) and (B) OEP)Ru(NO) SCH2CF3). The bimodal structure of some of the shifted bands is attributed to crystalline disorder and two possible orientations of the NO group. Conversion percentages are estimated as 1 and 1.5% for (A) and (B), respectively. Reproduced from Ref. (39) with permission of the Royal Society of Chemistry.

The situation concerning the local susceptibility is not fundamentally different in UCua sPdi.s. The agreement with NMR in the short-range correlation limit is not as good as for UCu+Pd, but still much better than for long-range correlations. In this material considerable crystalline disorder should be present and the result is more straightforward. 

In summary, the (xSR results together with the NMR data imply that a broad distribution of Kondo temperatures is present in UCus- Pd supporting a disorder-driven NFL state. This need not be coimected to marked crystalline disorder. A cooperative rather than a single-ion mechanism appears to be present. Only a small portion of moments is spin frozen in UCu4Pd, if at all. 

Doping carbon nanotubes with nitrogen atoms at lower concentrations than 6.5 wt% induce crystalline disorder in the graphene sheets, as well as an excess of electron donors on the nitrogen-rich areas may result in a more reactive structure compared to pure carbon nanotubes. For nitrogen-doped carbon nanotubes (N-MWCNT) two types of C-N bonds... 

The chemical nature of these materials has been well established using a variety of techniques, including NMR spectroscopy and elemental analysis. All analytic data are consistent with the formation of anion free systems, that is, the Pp5 which is present in the original complexes, [M(bipy)3](PF5)2, is no longer present in the electrocrystals. All of the data are consistent with the formation of pure [M(bipy)3]° materials. Unfortunately, it has not been possible yet to resolve the crystalline structure of any of these. They diffract and clearly show that the three materials are isomorphous. Unfortunately, all the samples that have been generated thus far seem to have too much crystalline disorder, precluding their complete structural solution. However, preliminary conductivity measurements have been conducted, and these suggest that the materials act as metallic conductors, vide infra. 

Both melting temperature (T ) and crystallization temperature (7 ) decrease with the increase in the PSSA content in the membranes. The reduction in is an indication of a crystalline disorder, which is confirmed by the reduction in the degree of crystallinity of the membranes with the increase in the PSSA content. The... 

One can imagine that the Pt2Ru4(CO)ig cluster compound is the intermediate in the reaction (2). The reaction can be further made via chemical decomposition of the compound to generate the bimetallic nanocatalyst. Indeed, Nuzzo et al. demonstrated that mixed Pt-Ru nanoparticles, with an extremely narrow size distribution (particle size 1.4 ran), were obtained. The Pt-Pt, Pt-Ru, and Ru-Ru coordination distances in the precursor (2.66, 2.64, and 2.84 A) changed to 2.73, 2.70, and 2.66 A, respectively, on the mixed-metal nanoparticles supported onto carbon black, with an enhanced crystalline disorder, as revealed by X-ray absorption fine stmcture (XAFS) spectroscopy. However, this example, using a controlled pyrolysis onto a designed molecirlar cluster, succeeds... 

The term solvatomorphism refers to those systems where the crystal structures of the substance are also defined by different unit cells, but where these unit cells differ in their elemental composition through the inclusion of one or more molecules from the solvent [151]. Water is the solvent that forms the largest number of solvatomorphic solids which are known as hydrates. The presence of the water molecules influences the intermolecular interactions (affecting the internal energy and enthalpy) and the crystalline disorder (entropy), and consequently the free energy, thermodynamic activity, solubihty, dissolution rate, stabifity and bioavailabihty [152]. 

BordaUo HN, Zakharov BA, Boldyreva EV, Johnson MR, Koza MM, Seydel T, Fischer J (2012) Application of incoherent inelastic neutron scattering in pharmaceutical analysis relaxation dynamics in phenacetin. Mol Pharm 9 2434-2441 Bptker JP, Karmwar P, Strachan CJ, Cornett C, Tian F, Zujovic Z, Rantanen J, Rades T (2011) Assessment of crystalline disorder in cryo-milled samples of indomethacin using atomic pairwise distribution functions. Int J Pharm 417 112-119 Boutonnet-Fagegaltier N, Menegotto J, Lamure A, Duplaa H, Caron A, Lacabanne C, Bauer M (2002) Molecular mobihty study of amorphous and crystalline phases of a pharmaceutical product by thermally stimulated current spectrometry. J Pharm Sci 91 1548-1560 Bras AR, Noronha JP, Antunes AMM, Cardoso MM, Schdnhals A, Affouard Fdr, Dionfsio M, Correia NIT (2008) Molecular motions in amorphous ibuprofen as studied by broadband dielectric spectroscopy. J Phys Chem B 112 11087-11099... 

Conformational class Extended Collapsed Random coiled Crystalline Disordered Liquid-like... 

Fig. 49 Creep rate spectra of PET demonstrating the changes in dynamics of initially amorphous polymer in the course of its cold crystallization by the thermal treatments for 3 h at indicated temperatures (formation of the peculiar states of inter-crystalline disordered regions)...

Figure 2.13 shows the X-ray diffraction pattern after 20 hours of milling MgCl in the presence of TiCl. The lattice disorder of the milled solid is apparent from the shape of the X-ray pattern and is due to the disorder in the packing of the chloride anions. Ball-milling time is important in determining the amoxmt of crystalline disorder obtained in the solid. Catalyst activity increases rapidly with ball-milling time up to about 20 hours (160 kg PE/g Ti) and reaches a maximum activity after about 80 hours (250 kg... 

Two kinds of crystalline disorder can be identified in XRD data. The disorder of the first kind refers to the imperfections... 

Figure 2.7 Global fitting of the data from a highly crystalline PET sample. The scan is resolved into crystalline peaks (sharp peaks), and two broad scattering, one due to the amorphous phase (the lower background line) and the other due to crystalline disorder (hatched area). Polizzi et al. [49]. Reproduced with permission of John Wiley and Sons.

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