Thursday, 29 January Chair: Prof. Joel Mesot (Director, Paul Scherrer Institute, Switzerland) Committee: Prof. Sine Larsen (Copenhagen), Prof. Thomas Schulthess (ETH Zurich), Dr. Mike Rowe (NIST Washington), Prof. Mike Klein (Philadelphia), Prof. Richard Jones (Sheffiel Professor C.N.R. Rao, FRS, Chair of India’s Nano Mission and Professor Robert McGreevy at ISIS earlier this month. Installation of Ar tanks to reduce scatter First call for proposals, deadline 31 Oct 2014 Part-funding of studentships Must have a facility development component Diffraction, Spectroscopy, Magnetism, Modelling and Theory Felix Fernandez-Alonso ISIS Molecular Spectroscopy Science Meeting The Cosener’s House, 29-30 January 2015 Molecular Spectroscopy at ISIS Xpress Access International Review - TOSCA (with MAPS & MARD epubs.stfc.ac.uk/work/1 1216706 TOSCA Upgrade - Primary Spectrometer 1 Situ, Operando & Simultaneous Techniques International Review - IRIS & OSIRIS VESUVIO: Frontiers & Horizons *Y iel (wt%)=(dry carbon weigh/ precursor weigh)*100 *Yiel (wt%)=(dry carbon weigh/ precursor weigh)* 100 *Yiel (wt%)=(dry carbon weigh/ precursor weigh)* 100 CO, adsorption isotherms at 298 K Immersion calorimetry into different liquids J. Silvestre-Albero et al. ChemComm 47, 6840-6842 (2011 Carbon molecular sieves vs. MOFs materials J. Silvestre-Albero et al. ChemComm 47, 6840-6842 (2011) Carbon molecular sieves vs. MOFs materials J. Silvestre-Albero et al. ChemComm 47, 6840-6842 (2011 Carbon molecular sieves vs. MOFs materials J. Silvestre-Albero et al. ChemComm 47, 6840-6842 (2011) Regeneration of the carbon molecular sieves M. Casco etal., Chem. Mater. DOI: 10.1021/cm5042524 (2015) Rutherford Appleton Laboratory - ISIS (UK) A large family of different types of fuel cells has been developed - here are a few examples from Wikipedia ILL methods at the ILL: Figure replotted and modified after Jobic, et al, Microporous and Mesoporous Materials (2007, “Long-range” diffusion constant obtained from different methods Figure 1 | Proton trapping in BYZ20. a, Long-range proton diffusivity exhibits downward curvature, as expressed in equation (3) (red line) with parameters given in Table 1. Red circles and triangles denote, respectively, the proton diffusivity and the ambipolar diffusivity between proton and deuterium determined by a.c. impedance spectroscopy (ACIS). The trap-free proton diffusivity calculated from the proton-dopant association (trapping) model (blue line) matches that determined from a neutron spin-echo (NSE) experiment (blue open circles"). b, Apparent activation energies for proton diffusion and constant activation energy for association-free proton diffusion. ¢, Trapped and trap-free proton concentrations computed from the proton-dopant association model, equation (2) and the experimentally measured total proton concentration (see Supplementary Information for full description of analysis methodology). Proton trapping in BaZrg gZrg 03H, > Luminescence emission spectrum Haro-Gonzales, Karlsson, Bettinelli et al., Solid State lonics 247-248 (2013) 94-97 Luminescence spectroscopy of Eu** in BaZrg 9¥o 999EUo,99103Ho 1 Luminescence emission spectrum Haro-Gonzales, Karlsson, Bettinelli et al., Solid State lonics 247-248 (2013) 94-97 Luminescence spectroscopy of Eu** in BaZry 9Y9.999EUp.00103Ho.1 Proton diffusivity varies with dopant Literature data over proton conductivities Strong Raman bands reveal local structural distortions Karlsson etal., Chem. Mater. 20 (2008) 3480 Fourier density maps at cuts of z = 0, showing missing positive scattering density attributed to D Neutron diffraction on hydrated Baln,Zr,_,O3_,/> (x = 0.50) Inelastic neutron scattering (O-H wag region) on) Infrared spectroscopy (O-H stretch modes) Work in progress / L. Mazzei, S. F. Parker, D. T. Adroja, M. Karlsson Low-frequency bands - fundamentals or not? Preliminary analysis of the spectra suggests: Recent INS (Merlin) results on hydrated Baln,Zr, ,O3_,;> (x = 0.50) Centre of mass distributions for butane (blue) and Methane (green) in silicalite Track the time evolution of a system by numerically solving the equations of motion for each particle (having chosen model carefully) Measuring surface correlation Structures from lineshape analysis Angw Chem Int Ed 52, 5085-8 (2013) Experimental barrier: 50 +3 meV Friction coefficient, n =2.0 ps Pyrrole/Cu(111) — quantum influences ‘,> H Aromatic adsorbates — benchmarking vdW DFT Soft Confinement Nanoparticles >Assembly of nanoparticles at fluid interface induced by capillary interactions *FB, Chacon, Tarazona & Tay, Phys. Rev. Lett. *FB, Chacon & Tarazona, Phys. Chem. Chem. Phys. *Armstrong and FB, J. Chem. Phys. (2013) - SPC/E water *Romer, Lervik and FB, J. Chem. Phys. (2012) * Thermostats VMiean-square displacement Neutron experiment (femperafure scan) Neutron Spectroscopy of Framework Materials Beyond Vibrations: Stochastic Phenomena Ice V / XIll phase transition at ambient pressure T. F. Whale, S.J. Clark, J. L. Finney, C.G. Salzmann, J. Raman Spectrosc., 44 (2013) 290 T. L. Malkin, B. J. Murray, A. V. Brukhno, J. Anwar, C. G. Salzmann, Proc. Natl. Acad. Sci. USA, 109 (2012) 1041-1045 )IFFaX (Treacy etal.) ina least-square environment P-(zero order)=0.72, @(1st order)=0.677, (2nd order)=0.670 T. L. Malkin, B. J. Murray, C. G. Salzmann V. Molinero, S.J . Pickering, T. F. Whale, accepted B.J. Murray, C. G. Salzmann, A.J. Heymsfield, S. Dobbie, R. R. Neely, C.J. Cox, submitted Tendency to stay in cubic or hexagonal sequences Still a long way to perfect ice Ic! Fic. 3, Examples of trigonal ice crystal shapes observed in the cirrus layer. B.J. Murray, C. G. Salzmann, A.J. Heymsfield, S. Dobbie, R. R. Neely, C.J. Cox, submitted Subtle structural differences and local density fluctuations in the ice | family beyond the first coordination shell. The spectroscopic signature of stacking disorder in ice ew technique available for characterising ice Isd in the lab but also for remote or even telescopic applications. Correlations with results from other techniques Structural relaxation of low-density amorphous ice J.J. Shephard, }.S.0O. Evans, C. G. Salzmann, J. Phys. Chem. Lett., 4 (2013) 3672-3676 Decoupled (OD) stretching modes of ASW (FT-IR) J.J. Shephard,}.S.O. Evans, C.G. Salzmann, J. Phys. Chem. Lett., 4 (2013) 3672-3676 Leeds Why (Nuclear) Quantum Effects Potential energy surface of the proton along the OH bond in ice Square modulus of the proton wave function Momentum distribution of the proton is a probe of the local environment .... ..or a probe of the force acting on the proton How to measure momentum distributions using the VESUVIO spectrometer at ISIS How to measure momentum distributions using the VESUVIO spectrometer at ISIS-II Note: in real experiments there is an additional broadening due to resolution and smal deviations from the purely “impulsive “ regime Compton profile of Na; p- resolution=13% S. Huotari et al, PRL 105, 086403 (2010) Protons, using VESUVIO at ISIS Electrons, using ID16 at ESRF How do we measure momentum distributions and kinetic energies of..? The shapes at two temperatures (180 K — protein does not work ) and (290 K protein works) have the same area, same center, same variance (<Ek>), but — different underlying potentials... The shapes of Neutron Compton profiles is directly related to potential and mean force These curve shapes look very different but have the same area, same center, same width (variance--- <Ek>) Determine o and <Ek> by numerical integration Two samples of ice at the same temperature, one doped with KOH 0.01 mol/| Shape analysis -non parametric way: Come and Do a VESUVIO Experiment..? Kimberly Kurtis, School of Civil Engineering Georgia Institute of Technology Atlanta, Georgia NIST model - Fraction of connected capillary pores. Bentz and Garboczi, Cem. and Conc. Res. 21,325 (1991). White spheres are hydrogen atoms, red are water oxygen, purple are layer oxygen, green are silicon, light blue are layer calcium, and yellow are interlayer calcium. Water molecules are highlighted with a larger size compared to the other elements in the model. Why are greener cements bett Neutrons tomography Benedict Lenhoff, BSc thesis, Johan Jacobsen, Solveig Hedal and Casper Madsen MSc thesis Peterson, Fratini, and many others... Why are MOFs important: What are Metal-Organic Frameworks? Synchrotron Infrared (IR) Spectroscopy Inelastic Neutron Scattering (INS) ¢ Shows possible phase transition, with the same deformed 6MR as ZIF-7-Ill. ‘Department of Engineering Science, University of Oxford, Department of Chemistry, University of Turin ‘Department of Engineering Science, University of Oxford, "ISIS Facility, Rutherford Appleton Laboratory, 3Diamond Light Source, Harwel Campus, “Department of Chemistry, University of Turin, Department of Materials Science and Metallurgy, University of Cambridge. M. R. Ryder,’” B. Civalleri,* T. D. Bennett,> S. Henke,> S. Rudic,” Terahertz Vibrations in Metal-Organic Frameworks: From Gate-O pening Phenomenon to Shear-Driven Structural Instability Our work shows, for the first time, that collective vibrations and low-energy THz modes offer insights into many possible and competing pathways governing unique physical mechanisms in ZIFs, including gate-opening and breathing phenomena, phase transitions, and onset of shear-induced structural instabilities. The results are very promising as a selection of these physical phenomena have recently been observed experimentally, confirming the validity and robustness of ow computational approach. The methodologies being developed here can be employed for studying other families of MOFs and associated framework materials, especially for predicting and tuning their multifunctional properties central to emerging technological applications [2]. Technical details: L.C. Pardo et al. Phys. Rev. E. 84, 046711 (2011); L.C Pardo et al. J. Phys.: Conf: Ser. 325, 012006 (2011) Real data fits: The program has been already used in many application ranging from astronomy (G. Sala et al.The Astrophysical Journal, 752:158, 2012), to QENS data (M. Rovira-Esteva et al. Phys. Rev. B_ 81(9) 092202, 2010), diffraction (M. Rovira-Esteva et al. Phys. Rev. B 84, 064202, 2011) or dielectric spectroscopy (J. C. Martinez et al. J. Phys. Chem. B 114 6099, 2010) ‘aculty of Engineering and the Environment, University of Southampton, Highfield, Southampton, $017 1BJ, UK; * SIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didoot Oxon OX11 0QX, UK XinLieo!, LinaChi!, Stewart E Parker, Martin, 0, Jones’, Zheng Jiang!* Application of indastic neutron scattering to studies of CO, reforming of methane over bimetallic Ni-Co/AL O,catalyst INS spectra of cyclopentanone solutions in CCl,. The bands marked with arrows present concentration-dependent intensities, an effect ascribed to the presence of a sel! equilibrium based on C-H---O hydrogen bonds. sociation The Raman spectrum of cyclopentanone, in the carbonyl stretching mode (vC=O) region, presents a band envelope composed of twe individual bands. The presence of this pair of bands can be interpreted in terms of a intermolecular association through hydrogen-bondin; to the carbonyl oxygen atom. The higher wavenumber band component is assigned to the free carbonyl group, and the lower wavenumbe band component is assigned to the hydrogen bonded carbonyl group. lonic liquids are of interest to chemistry and material sciences because of their designer properties. Protonated ionic liquids (PILs) are excellent proton carriers in fuel cell electrolytes. PILs are formed by the transfer of a proton from a Brgnsted acid to a Brgnsted base, which means they have a proton available for the formation of hydrogen bonding. Hydrogen bond is a strong directional inductor compared to the interaction of other forces, as Van der Waals interactions, and it has a high relevance in ionic liquid features. But, there is a lacuna in our knowledge of these compounds. In order to separate out different types of molecular motion and understand the contribution of individual hydrogen groups on the N and C atoms, we have studied the proton transfer in a structurally simples alkylammonium nitrate ionic liquids, [CH;NH,][NO;] and [(CH,),NH,][NO,] and the partially deuteriated analogues, [CH,;ND3][NO,] and [(CH3),ND,][NO,]. | have submitted a proposal following the results discussed in this poster . Aim of this proposal is to perform a temperature dependent QENS study of ethylammonium nitrate and its partially deuteriated analogue ([Et,NH,][NO,]), which will permit to characterise the classical hopping mechanism in the picosecond time domain. The MCL is part of the ISIS support lab team to provide support for beamline experiments. The Materials Characterisation Laboratory boasts a wide range of instrumentation, detailed below, for determining sample structure, screening and purity, as well as studying physical properties of materials. For more information or to book instrument time please contact Lab Manager Dr Gavin Stenning directly on gavin.stenning@stfc.ac.uk Hiden Isochema IGA - The hydrogen and catalysis lab at ISIS offers a range of equipment optimised for the study of hydrogen storage materials and catalysts. It features appropriate ventilation for working with pressurised H, gas and other flammabl gasses. Instrumentation is available to characterise H, storage materials including adsorption and desorption isotherms, porosity measurements and H, uptake. Spectroscopic equipment is also available for sample characterisation. For more information please contact Dr James Taylor (james.taylor@stfc.ac.uk). ISIS Molecular Spectroscopy Science Meeting, 29th & 30th January 2015, The Cosener’s House, Abingdor J.P. de Vicente1.2, F. Demmels, F. Sordo12, F. Fernandez-Alonso? Implementation of a Silicon Energy Analyser on McStas: The Way Forward for OSIRIS Figure 1 (a) Density and (b) radial distribution functions, G(r), of LDA, UHDA and vHDA. Adapted from Loerting et. al.. [3] and Salzmann et al.. [5] | acob |. Shephard!, A. Parmentier,2 G. Romanelli,2 R. Senesi,? C. Andreani,? Christoph G. Salzmann 1 Department of Chemistry, University College London, London, UK, email: c.salzmann@ ucl.ac.uk 2 Department of Physics and NAST Centre, University of Rome Tor Vergata, Rome, Italy The above figure shows the NEMD simulation setup we employ, whereby the regions shown in red and blue are subjected to velocity rescaling to enforce a “hot” and “cold” temperature respectively, thus driving the system into a steady state temperature gradient. Microscopic interpretation As advances in technology push the scales of electronic devices to ever smaller domains, it has become of great importance to understand heat transport at small scales in an effort to manage the waste heat produced by such devices. Water is a working fluid in not many industrial processes and so understanding its thermal properties is of particular interest. We employ both non-equilibrium molecular dynamics (NEMD) and equilibrium Green-Kubo, simulations in order to investigate the particularly novel phenomena of thermo-orientation, which has been shown to be present in both polar and non-polar fluids(1),(2). (Leff) The electric field as a function of temperature gradient for temperatures; 500 K, 575 K, 650 K, 725 K, 800 K and 1000 K. (Bottom left) The Fourier transform of the heat-flux auto-correlation (solid lines), polarisation auto-correlation (dashed lines) and the total overlap of the two functions as a function of temperature (inset figure). We have used the TIP4P/Ice? water model to study the thermal conductivity (TC) of Ice Ih, VI, VIl and a high pressure plastic phase (Fig.1). We use two approaches to compute the thermal conductivity; Equilibrium Molecular Dynamics (Green-Kubo method) and Non-Equilibrium Molecular Dynamics. We report results of the vibrational density of states, which provide a direct link to experiments, and highlights the different vibrational behaviour of the ice phases investigated here. Our results show that state of the art classical models strongly underestimate the thermal conductivity of the phases investigated here, except for ice VI, where we find guantitative agreement with exnverimental data. CONCLUSIONS 1) Rigid non-polarizable models underpredict the TC of ice Ih and ice VII 2) The computed TC for ice VI agrees with available experimental data 3) Our results show qualitative agreement with available experimental data in low energy transfe' region 4) The thermal conductivity of ice VII and plastic ice is very similar. This result suggests that hydrogen bonding does no play a significant role in determining the TC of high pressure phases. Going beyond lithium: simultaneous NMDs of H, C and O in the squaric acid across the order-disorder phase transition at T=373K 'School of Science and Technology, Nottingham Trent University, Nottingham NGI1 8NS, United Kingdom ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 OQX, United Kingdom * e-mail: matthew.krzystyniak@stfc.ac.uk Figure 6: SAXS (circles) and SANS (triangles) profiles from TiC-CDCs chlorinated at different temperatures; 600°C (blue), 800°C (red) and 900°C (black). Solid lines are best fit to the Gibaud model, which takes into account macro and micropore radius. ‘igure 4: Nitrogen sorption isotherms for TiC-CDC samples. Figure 5: Pore size distributions (PSD) obtained by application of the NLDFT (left) and DFT (right) pore filling model. Markers are hollow for adsorption branches and solid for \olume-weighted average pore size was calculated from pore size distributions. Deviations of average pore size lesorption branches. between the different models (NLDFT and DFT) was evident. The L] in Brenner-Stuart requires a long range interaction (Verlet cut of 4.7 0) to obtain smooth barrier and even so the barrier is about an order of magnitude lower !!! Comparison with classical simulation using the empirical Brenner-Stuart potentials The strong indications of the untapped potential of Carbon-based nanostructured materials as next-generation sorbents come mainly from simulation and theoretical work [1]. Dispersive interactions among the various carbon nanostructures (graphene, nanotubes, etc) as well as with guest molecules (H2, C02, etc) are at the core of the relevant physical mechanisms involved. However, the vast majority of the “in-silico” studies rely on effective pairwise descriptions of the dispersive forces (Lennard- J ones). Recent developments of new van-der-Waals DFT functionals [2] provide a convenient starting point to attain a more accurate representation. By making recourse of the SCARF-RAL cluster we have calculated the energy barriers involved in a specific type of stacking fault in graphite using a dispersive DFT functional. The calculations agree well with the experimental data but, the comparison with the standard pairwise potential calculations reveals a discrepancy of an order of magnitude. We show here our ongoing study of the limits as well as of possible improvements of classical pairwise modelisations of the interlayer interactions. R. Fernandez-Perea!, C. Cabrillo?, S. Mukhopadhyay2, F. Fernandez-Alonso2, and F. J. Bermejo! nstituto de Estructura de la Materia, IEM-CSIC, Serrano 123, 28006 Madrid, ISIS Pulsed Neutron and Muon Source, RAL, Chilton, Didcot, Oxfordshire 0X11 0QX, United Kingc Towards a better modelisation of carbon-based nanomaterials Conclusions: bibiliogratia: [1] S. Patchkovskii et al., Proc. Nat. Acad. Sci. (USA) 102, 10439 (2005); G. Mpourmpakis, E. Tylianakis and G. E. Froudakis, Nanoletters 7, 1893 (2007); G. K. Dimitrakis, E. Tylianakis and G. E. Froudakis, Nanoletters 8, 3166 (2008); Y.F. Zhao et al., Phys. Rev. B 78, 144102 (2008); S.S. Han, Chem. Comm. 36, 5427 (2009); Z.M. Ao etal., Solid State Comm. 149, 1363 (2009); Tylianakis and G.E. Froudakis, |. Phys. Chem. Lett 1, 2459 (2010). [2] Graziano etal.,). Phys.: Condens. Matter 24 424216 (2012) [3].R.B.Telling and M.|. Philosophical Magazine Letters 83, 411 (2003) that in ordinary Portland cement. Barroso-Bujans et al., ACS Macro Letters 1, 550 (2012)
THE PROSPECT OF NEUTRON SCATTERING IN THE 21 ST CENTURY: A POWERFUL TOOL FOR MATERIALS RESEARCH. Over the last 60 years research reactors (RRs) have played an important role in technological and socio-economical development of mankind, such as radioisotope production for medicine, industry, research and education. Neutron scattering has been widely used for research and development in materials science. The prospect of neutron scattering as a powerful tool for materials research is increasing in the 21 st century. This can be seen from the investment of several new neutron sources all over the world such as the Spallation Neutron Source (SNS) in USA, the Japan Proton Accelerator Complex (
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We report an inelastic neutron scattering (INS) study of H 2 molecule encapsulated inside the fullerene C 60 which confirms the recently predicted selection rule, the first to be established for the INS spectroscopy of aperiodic, discrete molecular compounds. Several transitions from the ground state of para-H 2 to certain excited translation-rotation states, forbidden according to the selection rule, are systematically absent from the INS spectra, thus validating the selection rule with a high degree of confidence. Its confirmation sets a precedent, as it runs counter to the widely held view that the INS spectroscopy of molecular compounds is not subject to any selection rules.
The neutron is a unique probe for non-destructive investigations in materials science because, other than its nuclear sister particle, the proton, a neutron interacts only weakly with many common materials 1-4 . It interacts strongly with only a few of the chemical elements, the most prominent being hydrogen 5 . Moreover, a neutron senses the differences between isotopes of a given element and feels the magnetic fields it passes 6 . What has limited its application is that dedicated neutron sources such as research reactors or spallation sources are necessary to produce strong beams of free neutrons. Useful neutron beams mostly contain particles with energies corresponding to thermal or sub-thermal energies (also called "thermal" or "cold" neutrons) and are generated by moderating the fast neutrons created in nuclear reactions 3 . Such neutrons have wavelengths comparable to atomic spacings in solids and liquids, and kinetic energies matching those governing molecular and nuclear dynamics in condensed matter 2 . Consequently, these characteristics of neutrons are being extensively exploited in neutron scattering and imaging experiments. Imaging has gained importance among non-destructive techniques in materials research within the past decade due to the rapid development of digital detectors with improved spatial 7-10 and temporal 11,12 resolutions, as well as the development of new imaging concepts 6,13,14 that utilize more of the unique properties of neutron radiation than conventional neutron imaging did in the past.
A new synthetic scattering function aimed at the description of the interaction of thermal neutrons with molecular solids has been developed. At low incident neutron energies, both lattice modes and molecular rotations are specifically accounted for, ...
An understanding of the fundamental physics of the Earth's interior requires information about the phase transitions and thermodynamic properties of key mantle-forming mineral phases. Inelastic neutron scattering (INS) is an indispensable tool for determining key lattice dynamics properties like the phonon dispersion relation (PDR) and density of states, which govern a wide range of material behaviors including structural phase transitions, thermodynamic properties, elasticity, and melting. In this chapter we review recent reported studies involving INS and lattice dynamics calculations of geophysically important minerals. We also review recent applications of INS involving experimental and theoretical ab initio and atomistic studies of the phonon spectra and thermodynamic properties of minerals and of other novel phenomena like high-pressure phonon softening, structural phase transitions, pressure-induced amorphization, magnetic excitations, melting, etc. We discuss the current understanding of the dynamical behavior, thermodynamic properties, and phase transitions of key mantle components like the olivine and pyroxene end members forsterite and enstatite, the mineral zircon, important silica polymorphs, and magnesium oxide; recent results on water and ice; other complex silicates; hydrogen storage materials; etc. Inelastic neutron scattering and complementary techniques like inelastic X-ray scattering have been used to explore the high-pressure PDR and density of states of iron, diamond, and magnesium oxide; to study magnetic excitations; to estimate the magnetic contributions to thermodynamic properties; etc. The theoretical calculations enable fruitful microscopic interpretations of complex experimental data and provide an atomic-level understanding of vibrational and thermodynamic properties.
Slow neutrons have proved to be a very powerful probe for examining materials in general and hydrogenous materials in particular. In this article we review various neutron scattering techniques which have been utilised to investigate different aspects of a variety of hydrogenous materials. TranslationaUy as well as orientationally disordered materials, ferroelectrics, superconductors, metal-hydrogen systems, polymers and biological molecules have been chosen as illustrative examples.
Neutron crystallography has had an important, but relatively small role in structural biology over the years. In this review of recently determined neutron structures, a theme emerges of a field currently expanding beyond its traditional boundaries, to address larger and more complex problems, with smaller samples and shorter data collection times, and employing more sophisticated structure determination and refinement methods. The origin of this transformation can be found in a number of advances including first, the development of neutron image-plates and quasi-Laue methods at nuclear reactor neutron sources and the development of time-of-flight Laue methods and electronic detectors at spallation neutron sources; second, new facilities and methods for sample perdeuteration and crystallization; third, new approaches and computational tools for structure determination.
Soft materials, both polymeric and biologically relevant, are rich in hydrogen. By coincidence, neutrons have the unique capability of scattering differently from hydrogen (coherent scattering length of hydrogen, b H = -0.37 × 10 -12 cm) compared to its isotope deuterium (b D = 0.67 × 10 -12 cm). As a result of this marked difference in scattering power (contrast) between native hydrogenated materials and their counterparts synthesized from deuterated monomer units, neutron scattering techniques have proven to be powerful tools for the study of soft condensed matter systems. Here, we will discuss the small-angle neutron scattering (SANS) technique, which is presently playing a pivotal role in extracting unique structural information from intrinsically disordered systems.
The inelastic neutron scattering ͑INS͒ spectrum of the original benzylic amide ͓2͔catenane is recorded and simulated by a semiempirical quantum chemical procedure coupled with the most comprehensive approach available to date, the CLIMAX program. The successful simulation of the spectrum indicates that the modified neglect of differential overlap ͑MNDO͒ model can reproduce the intramolecular vibrations of a molecular system as large as a catenane ͑136 atoms͒. Because of the computational costs involved and some numerical instabilities, a less expensive approach is attempted which involves the molecular mechanics-based calculation of the INS response in terms of the most basic formulation for the scattering activity. The encouraging results obtained validate the less computationally intensive procedure and allow its extension to the calculation of the INS spectrum for a second, theoretical, co-conformer, which, although structurally and energetically reasonable, is not, in fact, found in the solid state. The second structure was produced by a Monte Carlo simulated annealing method run in the conformational space ͑a procedure that would have been prohibitively expensive at the semiempirical level͒ and is characterized by a higher degree of intramolecular hydrogen bonding than the x-ray structure. The two alternative structures yield different simulated spectra, only one of which, the authentic one, is compatible with the experimental data. Comparison of the two simulated and experimental spectra affords the identification of an inelastic neutron scattering spectral signature of the correct hydrogen bonding motif in the region slightly above 700 cm Ϫ1. The study illustrates that combinations of simulated INS data and experimental results can be successfully used to discriminate between different proposed structures or possible hydrogen bonding motifs in large functional molecular systems.
In this work we address the problem of multiple scattering and inelasticity corrections in neutron diffraction measurements for structural studies of molecular systems. A variety of pulsed neutron and reactor experiments was performed on hydrogenous samples under different experimental conditions. Monte Carlo simulations were carried out on the basis of a Synthetic Model to describe the neutron-molecule interaction, and they allowed a simultaneous evaluation of multiple, inelastic and beam attenuation processes into the samples. A very good agreement between measurements and simulations was obtained in all cases, for our demanding choice of samples and experimental conditions.
Current Opinion in Solid State and Materials Science, 2004
Ultra-small-angle neutron scattering is a powerful new tool to quantitatively characterize the morphology of materials on length scales from 0.1 to 50 lm. The technique has already been used on a wide range of materials from hydrogels to geologic specimens. The data reveal a surprising richness of previously undetected morphological features. (D.W. Schaefer), magama-lian@sns.gov (M.M. Agamalian).
Neutron scattering is a very high-performance method for studying the structure and dynamics of condensed matter with similar approaches in wide ranges of space and time, matching dimensions in space from single atoms to macromolecules and in time from atomic vibrations over crystal phonons to low-lying transitions in the microwave range, and to motions of large molecular units. Concerning the number and depth of physical concepts, neutron scattering may be compared to modern nuclear magnetic resonance. Neutrons have contributed essential results to the understanding of atomic and molecular processes and are, in this respect, complementary to other materials science probes. Among others, three properties of thermal neutrons make them especially appropriate for such work: the neutron mass is similar to atomic masses, and both neutron energies and the wavelengths of the neutron material wave match typical values for condensed matter. A further important feature of neutron scattering, making it especially valuable in biochemistry and polymer sciences, is that hydrogen and deuterium atoms very significantly and specifically contribute to the signal in both diffraction and spectroscopy. Additionally, neutrons are scattered at the nuclei and directly reflect the nuclear structure and motions. Results from neutron scattering are of great general interest. This paper aims to provide an introduction for chemists on a level understandable also to students and researchers who are not going to become part of the neutron community and will not be involved in the experiments, but shall be able to understand the basic concepts of the method and its relevance to modern chemistry. The paper focuses on basic theory, typical experiments, and some examples demonstrating the applications. As for many modern experimental techniques, the interpretation of the results of neutron scattering is based on theoretical models and requires a significant mathematical overhead. Most results are only meaningful when compared with computer simulations. For understanding this, in this paper, the theory of scattering is developed, starting with intuitive models and presenting typical concepts such as the scattering triangle, energy and momentum transfer, and the relation of inelastic and elastic scattering to space- and time-dependent information. The interaction of neutrons with matter, scattering cross sections, beam attenuation, and coherent versus incoherent scattering are explained in detail. Two further typical concepts that are not generally familiar to scientists outside the community are the use of wave and particle equivalence, and of handling results as a scattering function that depends simultaneously on momentum and energy transfers. The possibility of obtaining neutron beams for scattering experiments at a few research centers around high-performance sources is explained, and experimentally relevant features of research reactors and spallation sources are mentioned. As neutron experiments always have to deal with small flux and extended beams and shielding, experimental conditions are very far away from laboratory methods where handling of samples and instruments is concerned. Experimental details are given for making experiments more understandable and familiarizing the reader with the method. Related to this are extended possibilities for handling samples in a large variety of different environments. In a further part of the manuscript, a variety of techniques and typical instruments are presented, together with some characteristic applications bringing alive the theory developed so far. This covers powder diffraction and structure of liquid water, triple-axis spectrometers and lattice phonons, backscattering spectrometry and rotational tunneling, time-of-flight spectrometry, and simultaneously probing the energy and shape of low lying vibrations and diffusion, filter spectrometer and vibrational spectroscopy without selection rules, small-angle neutron scattering and protein unfolding, as well as micelles, neutron spin echo spectroscopy, and polymer dynamics.
We report an inelastic neutron scattering (INS) study of 2-amino-3-hydroxymethyl-1,3-propane diol (TRIS). The assignment of the experimental vibrational spectra measured using several incident neutrons' energies on HRMECS spectrometer has been made by means of DFT calculations. To simulate crystal environment both molecular cluster and solid state models were used. The study has been completed by an alternative approach, molecular dynamics (MD) calculations, done at the same level of the DFT theory. The INS spectra calculated with the solid state models (normal mode analysis, and MD) gave a better fit of the experiment than the cluster model. On the other hand, the peaks between 650 and 850 cm À1 in the experimental INS spectra assigned to OH torsional modes were reproduced better by the cluster calculations. The nature of the stretching frequency of unusually long O-H bond (1.012 Å ) was interpreted by means of MD calculations. The interpretation of the spectrum below 100 cm À1 was based on Fourier transform of the velocity autocorrelation function of centre of mass of a molecule of TRIS.
We present a new implementation of the program nMoldyn, which has been developed for the computation and decomposition of neutron scattering intensities from Molecular Dynamics trajectories (Comp. Phys. Commun 1995, 91, 191-214). The new implementation extends the functionality of the original version, provides a much more convenient user interface (both graphical/interactive and batch), and can be used as a tool set for implementing new analysis modules. This was made possible by the use of a high-level language, Python, and of modern object-oriented programming techniques. The quantities that can be calculated by nMoldyn are the mean-square displacement, the velocity autocorrelation function as well as its Fourier transform (the density of states) and its memory function, the angular velocity autocorrelation function and its Fourier transform, the reorientational correlation function, and several functions specific to neutron scattering: the coherent and incoherent intermediate scattering functions with their Fourier transforms, the memory function of the coherent scattering function, and the elastic incoherent structure factor. The possibility to compute memory function is a new and powerful feature that allows to relate simulation results to theoretical studies.
Antonio Romerosa
![Our work shows, for the first time, that collective vibrations and low-energy THz modes offer insights into many possible and competing pathways governing unique physical mechanisms in ZIFs, including gate-opening and breathing phenomena, phase transitions, and onset of shear-induced structural instabilities. The results are very promising as a selection of these physical phenomena have recently been observed experimentally, confirming the validity and robustness of ow computational approach. The methodologies being developed here can be employed for studying other families of MOFs and associated framework materials, especially for predicting and tuning their multifunctional properties central to emerging technological applications [2].](https://figures.academia-assets.com/115144391/figure_355.jpg)
![lonic liquids are of interest to chemistry and material sciences because of their designer properties. Protonated ionic liquids (PILs) are excellent proton carriers in fuel cell electrolytes. PILs are formed by the transfer of a proton from a Brgnsted acid to a Brgnsted base, which means they have a proton available for the formation of hydrogen bonding. Hydrogen bond is a strong directional inductor compared to the interaction of other forces, as Van der Waals interactions, and it has a high relevance in ionic liquid features. But, there is a lacuna in our knowledge of these compounds. In order to separate out different types of molecular motion and understand the contribution of individual hydrogen groups on the N and C atoms, we have studied the proton transfer in a structurally simples alkylammonium nitrate ionic liquids, [CH;NH,][NO;] and [(CH,),NH,][NO,] and the partially deuteriated analogues, [CH,;ND3][NO,] and [(CH3),ND,][NO,].](https://figures.academia-assets.com/115144391/figure_364.jpg)
![| have submitted a proposal following the results discussed in this poster . Aim of this proposal is to perform a temperature dependent QENS study of ethylammonium nitrate and its partially deuteriated analogue ([Et,NH,][NO,]), which will permit to characterise the classical hopping mechanism in the picosecond time domain.](https://figures.academia-assets.com/115144391/figure_365.jpg)
![Figure 1 (a) Density and (b) radial distribution functions, G(r), of LDA, UHDA and vHDA. Adapted from Loerting et. al.. [3] and Salzmann et al.. [5] | acob |. Shephard!, A. Parmentier,2 G. Romanelli,2 R. Senesi,? C. Andreani,? Christoph G. Salzmann 1 Department of Chemistry, University College London, London, UK, email: c.salzmann@ ucl.ac.uk 2 Department of Physics and NAST Centre, University of Rome Tor Vergata, Rome, Italy](https://figures.academia-assets.com/115144391/figure_371.jpg)
![The L] in Brenner-Stuart requires a long range interaction (Verlet cut of 4.7 0) to obtain smooth barrier and even so the barrier is about an order of magnitude lower !!! Comparison with classical simulation using the empirical Brenner-Stuart potentials The strong indications of the untapped potential of Carbon-based nanostructured materials as next-generation sorbents come mainly from simulation and theoretical work [1]. Dispersive interactions among the various carbon nanostructures (graphene, nanotubes, etc) as well as with guest molecules (H2, C02, etc) are at the core of the relevant physical mechanisms involved. However, the vast majority of the “in-silico” studies rely on effective pairwise descriptions of the dispersive forces (Lennard- J ones). Recent developments of new van-der-Waals DFT functionals [2] provide a convenient starting point to attain a more accurate representation. By making recourse of the SCARF-RAL cluster we have calculated the energy barriers involved in a specific type of stacking fault in graphite using a dispersive DFT functional. The calculations agree well with the experimental data but, the comparison with the standard pairwise potential calculations reveals a discrepancy of an order of magnitude. We show here our ongoing study of the limits as well as of possible improvements of classical pairwise modelisations of the interlayer interactions. R. Fernandez-Perea!, C. Cabrillo?, S. Mukhopadhyay2, F. Fernandez-Alonso2, and F. J. Bermejo! nstituto de Estructura de la Materia, IEM-CSIC, Serrano 123, 28006 Madrid, ISIS Pulsed Neutron and Muon Source, RAL, Chilton, Didcot, Oxfordshire 0X11 0QX, United Kingc Towards a better modelisation of carbon-based nanomaterials](https://figures.academia-assets.com/115144391/figure_382.jpg)
![Conclusions: bibiliogratia: [1] S. Patchkovskii et al., Proc. Nat. Acad. Sci. (USA) 102, 10439 (2005); G. Mpourmpakis, E. Tylianakis and G. E. Froudakis, Nanoletters 7, 1893 (2007); G. K. Dimitrakis, E. Tylianakis and G. E. Froudakis, Nanoletters 8, 3166 (2008); Y.F. Zhao et al., Phys. Rev. B 78, 144102 (2008); S.S. Han, Chem. Comm. 36, 5427 (2009); Z.M. Ao etal., Solid State Comm. 149, 1363 (2009); Tylianakis and G.E. Froudakis, |. Phys. Chem. Lett 1, 2459 (2010). [2] Graziano etal.,). Phys.: Condens. Matter 24 424216 (2012) [3].R.B.Telling and M.|. Philosophical Magazine Letters 83, 411 (2003)](https://figures.academia-assets.com/115144391/figure_383.jpg)
