Dynamical structural disorder

One of plausible candidates for the entropy source is a dynamic structural disorder in the HS phase, which should be settled down in the LS phase. The crystallographic data for [Mn(taa)] [11] provide a clue, i.e., the presence of C3 axis in the HS molecule. An Mn(III) ion in the 5E state is a well-known Jahn-Teller ion [19]. Since the C3 site-symmetry cannot lift the orbital degeneracy of the 5E term (Fig. 1(b)), it is likely that the Mn ion is subjected to the E e Jahn-Teller effect, which gives rise to three energetically equivalent deformation structures. The apparent C3 symmetry should be observed in a time-averaged structure over three deformed structures. 

Proton magnetic resonance spectroscopy and C nuclear magnetic resonance (NMR) spectroscopy have been reported to study the nature of water in hiunan SC (Foreman, 1976 Yamamura and Tezuka, 1989 Jokura et al., 1995). The H-NMR data are useful to study dynamic structural disorder of the intercellular lamellar Upid structure in the SC (Bezema etal., 1996). For further information on the use of NMR for investigating SC stmcture, refer to the review by Abraham et al. (1997). 

Molecular Motions and Dynamic Structures. Molecular motions are of quite general occurrence in the solid state for molecules of high symmetry (22,23). If the motion does not introduce disorder into the crystal lattice (as, for example, the in-plane reorientation of benzene which occurs by 60° jumps between equivalent sites) it is not detected by diffraction measurements which will find a seemingly static lattice. Such molecular motions may be detected by wide-line proton NMR spectroscopy and quantified by relaxation-time measurements which yield activation barriers for the reorientation process. In addition, in some cases, the molecular reorientation may be coupled with a chemical exchange process as, for example, in the case of many fluxional organometallic molecules. ... 

Tompa P (2009) Structural disorder in amyloid fibrils its implication in dynamic interactions of proteins. FEBS J 276 5406-5415... 

The NCP is a dynamic structure, even within the crystal. The diffraction from an NCP crystal is affected by disorder or motions of subunits, the individual amino... 

Recently, the PDF method was extended to describe the local dynamics of disordered materials (Dmowski W, Vakhrushev SB, Jeong I-K, Hehlen M, Trouw F, Egami T (2006) Abstracts American conference on neutron scattering, St. Charles, IL, 18-22 June 2006, unpublished). The total PDF is obtained by the powder diffraction method so that S(Q) includes both elastic and inelastic intensities. To determine the dynamics we have to use an inelastic neutron scattering spectrometer and measure the dynamic structure factor, S(Q,a>), over a large Q and co space, and Fourier-transform along Q to obtain the dynamic PDF (DPDF). While the interpretation of the DPDF is a little... 

Recently, the effects of static and dynamic structural fluctuations on the electron hole mobility in DNA were studied using a time-dependent self-consistent field method [33]. The motion of holes was coupled to fluctuations of two step parameters of a duplex, rise and twist (Fig. 1), namely the distances and the dihedral angles between base pairs, respectively. The hole mobility in an ideally ordered poly(G)-poly(C) duplex was found to be decreased by two orders of magnitude due to twisting of base pairs and static energy disorder. A hole mobility of 0.1 cm V s was predicted for a homogeneous system the mobility of natural duplexes is expected to be much lower [33]. In this context, one can mention several theoretical studies, based on band structure approaches, to estimate the electrical conductivity of DNA [85-87]. 

Because all of the coordinating atoms in a shell are not fixed in position at exactly R the term a2 in e accounts for the disorder in the interatomic distances. The term has contributions from dynamic (thermal) disorder and static disorder (structural). 

If the light emanating from an organic LED originates from the radiative decay of locally excited (molecular) states (see Fig. 11), we deal with molecular emission spectra. They, in general, differ from those of isolated molecules because the gas-to-solid shift, and resonance interactions must be taken into account [cf. Eq. (13)]. Moreover, they can reveal wider bands due to dynamical and structural disorder in the solid... 

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