TOSCA neutron spectrometer: The final configuration

Colognesi, D.; Celli, Milva; Cilloco, F.; Newport, Robert J.; Parker, Stewart F.; Rossi-Albertini, V.; Sacchetti, F.; Tomkinson, J.; Zoppi, M.

doi:10.1007/s003390101078

Cited by 190 publications

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“…25 Polycrystalline samples of ca. 1 g were held at 15 K for the downscattering experiments, while data taken on FCS were taken with the sample at 200 K in neutronenergy gain.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

et al. 2004

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The inelastic incoherent neutron scattering spectra of 1,3-cyclohexanedione (CHD) in its crystalline enol form and its cyclamer complexes with benzene and benzene-d 6 are compared with each other, with IR and Raman spectra and with the results of calculations using density functional theory (DFT). The crystal packing of the CHD enol is a linear hydrogen-bonded chain with conjugated donor and acceptor groups analogous to that found in peptide hydrogen bonding. The benzene complex is a closed hexameric hydrogen-bonded cycle. A DFT treatment is applied to the full hexamer of the benzene complex. The CHD chain is treated as a series of finite linear clusters by DFT, while the infinite one-dimensional chain and the three-dimensional crystal are treated by periodic DFT. Comparison is made with both the observed crystal structures and the vibrational spectra. The very good to excellent agreement of the computed vibrational spectra with experiment demonstrates that the models and computational treatments used are reliable. The theoretical treatment of the linear chain clusters exhibits a continuous change in structure with increasing chain length, converging to values near the observed structure. Emphasis is placed on the cooperative nature of hydrogen bonding in CHD as revealed by these systematic trends. The ability of DFT methods to treat hydrogen bonding in solids appears to be roughly as accurate as the crystal structure determinations.1,3-Cyclohexanedione (CHD) exists in its enol form in the solid state where it forms hydrogen-bonded chains with an antianti configuration having short (2.56 Å) O-O hydrogen bonding distances. 1 This structure is of interest for several reasons including the ordered hydrogen bonding arrangement, an orderdisorderphasetransitionthatinvolveshydrogenbondinterchange, 2-6 and indications derived from examination of crystal structures that CHD is an example of a resonance-assisted, cooperative hydrogen bonding network. [7][8][9][10][11][12][13] This cooperativity arises from the fact that when the enol of CHD forms a hydrogen bond, this polarizes the molecule such that the formation of an additional hydrogen bond with another CHD is more favorable. This may be thought of as due to an enhanced contribution of the ionic resonance form. When crystallized from benzene, this material forms a unique cyclamer structure (CHD 6 Bz) in which six CHD molecules form a syn-anti hydrogen bonded ring surrounding a central benzene molecule. 14 The related 1,3-cyclopentanedione (CPD) 15 forms an antianti linear chain structure very much like that of CHD. Methyl substitution of CPD or CHD can result in changes to the hydrogen-bonding pattern. 2-Methyl-CPD forms a linear chain with an anti-syn arrangement. 16 In this case the methyl-CHD molecules in a given linear chain all point in the same direction. This is in contrast to the anti-anti chain of CPD and CHD (Figure 1) where alternate molecules are oriented in opposite directions. The 2-methyl derivative of CHD has a structure similar to that of CHD 17 but t...

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“…25 Polycrystalline samples of ca. 1 g were held at 15 K for the downscattering experiments, while data taken on FCS were taken with the sample at 200 K in neutronenergy gain.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

et al. 2004

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“…To gain further insights into the macromolecular structure of confined PEO, INS measurements on PEO/GO, PEO/pR-GO, PEO/G, and their respective substrates were performed on the TOSCA spectrometer at 30 K. 16 One of the primary advantages of INS spectroscopy is that there are no hard selection rules and mode intensities can be directly related to the underlying vibrational density of states (VDOS). Therefore, spectral assignments can be performed on the basis of previous Raman and infrared studies.…”

mentioning

confidence: 99%

Macromolecular Structure and Vibrational Dynamics of Confined Poly(ethylene oxide): From Subnanometer 2D-Intercalation into Graphite Oxide to Surface Adsorption onto Graphene Sheets

et al. 2012

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ABSTRACT:In this work, high-resolution inelastic neutron scattering (INS) has been used to provide novel insights into the properties of confined poly(ethylene oxide) (PEO) chains. Two limits have been explored in detail, namely, single-layer 2D-polymer intercalation into graphite oxide (GO) and surface polymer adsorption onto thermally reduced and exfoliated graphite oxide, i.e., graphene (G) sheets. Careful control over the degree of GO oxidation and exfoliation reveals three distinct cases of spatial confinement: i) subnanometer 2D-confinement; ii) frustrated absorption and iii) surface immobilization. Case i) results in drastic changes to PEO conformational (800-1000 cm -1 ) and collective (200-600 cm -1 ) vibrational modes as a consequence of a preferentially planar zig-zag (trans-trans-trans) chain conformation in the confined polymer phase. These changes give rise to peculiar thermodynamic behavior, whereby confined PEO chains are unable to either crystallize or display a calorimetric glass transition. In case ii), GO is thermally reduced resulting in a disordered pseudo-graphitic structure. As a result, we observe minimal PEO absorption owing to a dramatic reduction in the abundance of hydrophilic groups inside the distorted graphitic galleries. In case iii), the INS data unequivocally show that PEO chains adsorb firmly onto the G sheets, with a substantial increase in the population of gauche conformers. Well-defined glass and melting transitions associated with the confined polymer phase are recovered in case iii), albeit at sensibly lower temperatures than those of the bulk.

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“…• , available on TOSCA neutron spectrometer 35 . The results presented correspond to the averages of the intensities calculated, and measured, at these two angles.…”

mentioning

confidence: 99%

Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics

Ulivi

Celli

et al. 2011

Phys. Rev. B

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TOSCA neutron spectrometer: The final configuration

Cited by 190 publications

References 0 publications

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

The Crystalline Enol of 1,3-Cyclohexanedione and Its Complex with Benzene: Vibrational Spectra, Simulation of Structure and Dynamics and Evidence for Cooperative Hydrogen Bonding

Macromolecular Structure and Vibrational Dynamics of Confined Poly(ethylene oxide): From Subnanometer 2D-Intercalation into Graphite Oxide to Surface Adsorption onto Graphene Sheets

Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics

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