Medium-range order

EXAFS information is restricted to the first or second coordination sphere around a central atom whereas WAXS (Wide-Angle X-ray Scattering) can yield information on short and medium range order up to 20 A. It has been applied, for instance, to the important polymeric chain ST material [Fe(Htrz)2trz](BF4) (Htrz= 1,2,4-triazole), in the LS and HS state and indicated the likely involvement of hydrogen bonding between the anion and the 4-H atom of the triazole ring [62]. 

Abstract Modern solid state nuclear magnetic resonance presents new powerful opportunities for the elucidation of medium range order in glasses in the sub-nanometer region. In contrast to standard chemical shift spectroscopy, the strategy presented here is based on the precise measurement and quantitative analysis of internuclear magnetic dipole-dipole interactions, which can be related to distance information in a straightforward manner. The... 

Presence of medium range order gives rise to another phenomenon observed in spectroscopy, known as Boson peaks. These arise from the quasi-local excitations sustained by regions in which such intermediate order (IRO) is present. Several studies have indicated the presence of anomalies of vibrational properties such as excess vibrational density of states at low energies observed at low temperatures. This manifests as Boson peaks in Raman spectra. The normalized Raman spectra in the low frequency region are shown in Figure 3.13 for the same glasses for which... 

Figure 6.3 presents the amorphous alloy obtained by Hirotsu et al. [6.17] with the help of high resolution TFM. Circles separate the regions of medium-range ordering (MRO) with the sizes 2 nm in the amorphous alloy Pd Cu Si. When annealing is performed below the crystallization temperature, the dimen-... 

P.H. Gaskell, M.C. Eckersley, A.C. Barnes, and P. Chieux, Medium-range order in the cation distribution of a calcium silicate glass, Nature 350, 675-677 (1991). 

M.C. Abramo, C. Caccamo, and G. Pizzimenti, Structural properties and medium-range order in calcium-metasilicate (CaSi03) glass a molecular dynamics study, J. Chem. Phys. 96, 9083-9091 (1992). 

L.P. Davila et al. Transformations in the medium-range order of fused silica under high pressure, Phys. Rev. Lett. 91, 205501-1-205501-4 (2003). 

This method provides unvaluable informations on the short and medium range order in disordered atomic architectures amorphous solids, glasses but also liquids or complexes in solution. The fast development and the economical importance of... 

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