Neutron Scattering Results

A detailed test of dynamic RPA requires a combination of static and dynamic neutron experiments involving investigations of the respective component dynamics. All three issues addressed in the introduction were investigated. We will start with the collective dynamics of a diblock copolymer and then address the single component dynamics. Finally, we will discuss aspects of the interface dynamics. The experiments were performed on diblock copolymers of the PE-PEE and PE-PEP type. In order to access the different dynamics a series of materials with different h-d labelUng was employed (see Table 6.1). 

This diblock copolymer does not undergo the order-disorder microphase separation the peak stays broad above 373 K, where the system is in the mean 

Sample 11 20% hPE-hPEE in dPE-dPEE Sample 111 20% dPE-hPEE in dPE-dPEE  

The general agreement between mean-field prediction and experimental results was excellent. Other than PE-PEE, PEP-PEE (sample VI) undergoes an ODT which is observed at 473 K. An analysis by the modified RPA theory due to Fredrickson [265] yields a strong stretching of the radii of gyration around the ODT and a temperature-dependent Flory-Huggins parameter  

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D. Comparison of MD and Neutron Scattering Results on Lipid Dynamics... 

Clearly, the best way to assess the ability of MD simulations to reproduce neutron scattering results is to compare measured and computed spectra directly, one on top of the other. 

Fig. 50. Small-angle neutron scattering results from different stars in a scaled form. The lines are the result of a fit with Eq. (94). Insert Related radial segment distribution functions obtained from a Fourier transformation of the theoretical scattering function. (Reprinted with permission from [150]. Copyright 1987 The American Physical Society, Maryland)...

Phys. Condens. Matter, 15, S1127 (2003). Self-Motion and the a-Relaxation in Glass-Forming Polymers. Molecular Dynamic Simulation and Quasielastic Neutron Scattering Results in Polyisoprene. 

There is a fundamental question concerning the nature of the self-motion of protons in glass-forming polymers. In Sect. 4.1 we have shown that the existing neutron scattering results on the self-correlation function at times close to the structural relaxation time r (Q-region 0.2t) with a KWW-like functional form and stretching exponents close to jSsO.5. 

Fig. 8.6. Inelastic neutron scattering results on PrBi. The different inelastic peaks correspond to different transitions between the CEF-levels. For comparison LaBi does not show the inelastic scattering.

Inelastic neutron scattering results for La Cs2 and Y Cs2 (Lebedkin et al., 1998a,b) also presented evidence of metal-to-cage vibrations at 180, 150, and 85 cm The interval from 100 to 200 cm in the Raman and FIR spectra of M Cs2 (M = divalent and trivalent metal atoms) can be regarded as a "metal-fingerprint" range. 

Fig. 10. Pair correlation functions obtained both from Car-Parrinello simulations and from experiments. The thick solid lines are simulation results obtained using a supercell with 64 water molecules. The thin solid lines are for the 32-water molecule simulation. The short-dashed line is from experimental neutron scattering results (Soper et al., 1997), and the long-dashed line is from an X-ray study. Reprinted with permission from Silvestrelli and Parrinello (1999).

Schimmel et al. [63] have conducted adsorption isotherm and inelastic neutron scattering studies of hydrogen adsorbed on various carbon adsorbents including SWNTs. By comparing the inelastic neutron scattering results for Hj on the SWNTs with those for interstitially loaded H2 on Cgg, they conclude that H2 cannot adsorb in the ICs of SWNTs. They explain that this occurs because the molecular size of H2 is too large to fit in the estimated size for the ICs. 

In Fig. 13 the neutron scattering result of a measurement on liquid RbgO is shown. 34) S(Q) is characterized by a pronounced decrease in the intensity of the main peak accompanied by a shift from 1.52 to 1.58 A. An additional peak arises at. 68 A, which corresponds to pair correlations at long distances around 920 pm in real space. Characteristic features of the ionic clusters are recognized in the pair... 

Fig. 13. Neutron scattering results for liquid Rb and RbgO at 320 K. S t) (a) measured structure factors S (Q) for Rb (dashed line) and RbgO (full line), (b) pair correlation functions g(r) for Rb (dashed line) and Rb60 (full line)...

H. Jobic, A. Tuel, M. Krossner J. Sauer (1996). J. Phys. Chem., 100, 19545-19550. Water in interaction with acid sites in H-ZSM-5 zeolite does not form hydroxonium ions. A comparison between neutron scattering results and ab initio calculations. 

The neutron scattering results can be directly compared with molecular dynamics simulations. A number of works [72-74] was devoted to molecular dynamic modeling of the orientational ordering in fullerite. Most of them used... 

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