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YMgNi4-based alloys exhibit reversible hydrogen absorption and desorption reactions at near room temperature. Here, we report that Co-substituted YMgNi4-based alloys exhibited higher hydrogen contents and lower hydrogen absorption and desorption reaction pressures than unsubstituted alloys. The effects of Co-substitution viewed from atomic arrangements were particularly clarified by synchrotron radiation powder X-ray diffraction, neutron diffraction, and inelastic neutron scattering. Powder neutron diffraction of the Co-substituted alloy at 5 MPa of D-2 pressure suggested the formation of gamma-phase deuteride (higher deuterium content) from beta-phase deuteride (lower deuterium content). However, no gamma-phase deuteride was observed in the unsubstituted alloys at 5 MPa. Therefore, the gamma-phase deuteride formation of the Co-substituted alloy at lower pressure led to higher hydrogen contents than the unsubstituted alloys. The combined results of powder neutron diffraction and inelastic neutron scattering suggested that the gamma-phase hydride of the Co-substituted alloy was continuously generated due to additional H atoms at the H atom sites in the beta-phase hydride because of the disordered H atomic arrangement involving H-H interactions. As a result, hydrogen absorption and desorption reaction pressures for the gamma-phase deuteride formation with higher hydrogen storage capacity were lowered.

The presence of active sites in metal-organic framework (MOF) materials can control and affect their performance significantly in adsorption and catalysis. However, revealing the interactions between the substrate and active sites in MOFs at atomic precision remains a challenging task. Here, we report the direct observation of binding of NH3 in a series of UiO-66 materials containing atomically dispersed defects and open Cu(I) and Cu(II) sites. While all MOFs in this series exhibit similar surface areas (1111-1135 m2 g-1), decoration of the-OH site in UiO-66-defect with Cu(II) results in a 43% enhancement of the isothermal uptake of NH3 at 273 K and 1.0 bar from 11.8 in UiO-66-defect to 16.9 mmol g-1 in UiO-66-CuII. A 100% enhancement of dynamic adsorption of NH3 at a concentration level of 630 ppm from 2.07 mmol g-1 in UiO-66-defect to 4.15 mmol g-1 in UiO-66-CuII at 298 K is observed. In situ neutron powder diffraction, inelastic neutron scattering, and electron paramagnetic resonance, solid-state nuclear magnetic resonance, and infrared spectroscopies, coupled with modeling reveal that the enhanced NH3 uptake in UiO-66-CuII originates from a {Cu(II)···NH3} interaction, with a reversible change in geometry at Cu(II) from near-linear to trigonal coordination. This work represents the first example of structural elucidation of NH3 binding in MOFs containing open metal sites and will inform the design of new efficient MOF sorbents by targeted control of active sites for NH3 capture and storage.

We report the reversible adsorption of ammonia (NH3) up to 9.9 mmol g–1 in a robust Al-based metal–organic framework, MFM-303(Al), which is functionalized with free carboxylic acid and hydroxyl groups. The unique pore environment decorated with these acidic sites results in an exceptional packing density of NH3 at 293 K (0.801 g cm–3) comparable to that of solid NH3 at 193 K (0.817 g cm–3). In situ synchrotron X-ray diffraction and inelastic neutron scattering reveal the critical role of free −COOH and −OH groups in immobilizing NH3 molecules. Breakthrough experiments confirm the excellent performance of MFM-303(Al) for the capture of NH3 at low concentrations under both dry and wet conditions.

The thermally activated dynamics of methyl groups are important for biochemical activity as they allow for a more efficient sampling of the energy landscape. Here, we compare methyl rotations in the dry and variously hydrated states of three primary drugs under consideration to treat the recent coronavirus disease (COVID-19), namely, hydroxychloroquine and its sulfate, dexamethasone and its sodium diphosphate, and remdesivir. We find that the main driving force behind the considerable reduction in the activation energy for methyl rotations in the hydrated state is the hydration-induced disorder in the methyl group local environments. Furthermore, the activation energy for methyl rotations in the hydration-induced disordered state is much lower than that in an isolated drug molecule, indicating that neither isolated molecules nor periodic crystalline structures can be used to analyze the potential landscape governing the side group dynamics in drug molecules. Instead, only the explicitly considered disordered structures can provide insight.

Inelastic neutron scattering (INS) is a widely used technique to study atomic and molecular vibrations. With the increasing complexity of materials and thus the INS spectra, being able to simulate the spectra from various atomistic models becomes an essential step and also a major bottleneck for INS data analysis. The conventional approach using density functional theory and lattice dynamics often falls short when the materials of interest are complex (e.g., defective, disordered, heterogeneous, amorphous, large-scale), for which molecular dynamics driven by an interatomic force field is a more common approach. In this paper, we demonstrate a method to directly convert molecular dynamics trajectories into simulated INS spectra, including not only fundamental but also higher order excitations. The results are compared with data collected on various representative samples from different neutron spectrometers. This development will open great opportunities by providing the key tool to perform in-depth analysis of INS data and to validate and optimize computer models.

We report the heterolysis of molecular hydrogen under ambient conditions by the crystalline frustrated Lewis pair (FLP) 1-{2-[bis (pentafluorophenyOboryl] phenyl -2, 2,6,6-tetrame-thylpiperidine (KCAT). The gas-solid reaction provides an approach to prepare the solvent-free, polycrystalline ion pair KCATH2 through a single crystal to single crystal transformation. The crystal lattice of KCATH2 increases in size relative to the parent KCAT by approximately 2%. Microscopy was used to follow the transformation of the highly colored red/orange KCAT to the colorless KCATH2 over a period of 2 h at 300 K under a flow of H-2 gas. There is no evidence of crystal decrepitation during hydrogen uptake. Inelastic neutron scattering employed over a temperature range from 4-200 K did not provide evidence for the formation of polarized H-2 in a precursor complex within the crystal at low temperatures and high pressures. However, at 300 K, the INS spectrum of KCAT transformed to the INS spectrum of KCATH2. Calculations suggest that the driving force is more favorable in the solid state compared to the solution or gas phase, but the addition of H-2 into the KCAT crystal is unfavorable. Ab Initio methods were used to calculate the INS spectra of KCAT, KCATH2, and a possible precursor complex of H-2 in the pocket between the B and N of crystalline KCAT. Ex-situ NMR showed that the transformation from KCAT to KCATH2 is quantitative and our results suggest that the hydrogen heterolysis process occurs via H-2 diffusion into the FLP crystal with a rate-limiting movement of H-2 from inactive positions to reactive sites.

Heat and charge transport properties of the metallic unconventional clathrate BaNi2P4, hosting Ba cations in oversized Ni8P16 cages, are investigated. A novel method of single crystal growth was de...

The thermal neutron scattering cross-section of a solid depends on the energy (or wavelength) of the incident neutrons. Devising a method to calculate the energy dependence from first principles, without the approximations built in the scattering theory, has been a major undertaking in nuclear engineering. Here, we demonstrate such a calculation method using the program OCLIMAX. Our approach eliminates various approximations and limitations involved in a regular calculation with the LEAPR module of NJOY code, and the results are compared with available experimental and theoretical data. It is also demonstrated how additional insight can be obtained from the calculated full dynamical structure factor. The results reported here show the great potential and excellent platform provided by OCLIMAX for future development in the study of neutron thermalization in solid materials for different applications.

Ceria has been used as a hydrogenation catalyst especially in selective alkyne hydrogenation, but the reaction mechanism regarding the role of different surface hydrogen species remains unclear. In...

Recently, there have been renewed interests in exploring new catalysts for ammonia synthesis under mild conditions. Electride-based catalysts are among the emerging ones. Ruthenium particles supported on an electride composed of a mixture of calcium and aluminum oxides (C12A7) have attracted great attention for ammonia synthesis due to their facile ability in activating N2 under ambient pressure. However, the exact nature of the reactive hydrogen species and the role of electride support still remain elusive for this catalytic system. In this work, we report for the first time that the surface-adsorbed hydrogen, rather than the hydride encaged in the C12A7 electride, plays a major role in ammonia synthesis over the Ru/C12A7 electride catalyst with the aid of in situ neutron scattering techniques. Combining in situ neutron diffraction, inelastic neutron spectroscopy, density functional theory (DFT) calculation, and temperature-programmed reactions, the results provide direct evidence for not only the presence of encaged hydrides during ammonia synthesis but also the strong thermal and chemical stability of the hydride species in the Ru/C12A7 electride. Steady state isotopic transient kinetic analysis (SSITKA) of ammonia synthesis showed that the coverage of reactive intermediates increased significantly when the Ru particles were promoted by the electride form (coverage up to 84%) of the C12A7 support rather than the oxide form (coverage up to 15%). Such a drastic change in the intermediate coverage on the Ru surface is attributed to the positive role of electride support where the H2 poisoning effect is absent during ammonia synthesis over Ru. The finding of this work has significant implications for understanding catalysis by electride-based materials for ammonia synthesis and hydrogenation reactions in general.

Spin–Phonon coupling plays a critical role in magnetic relaxation in single-molecule magnets (SMMs) and molecular qubits. Yet, few studies of its nature have been conducted. Phonons here refer to both intermolecular and intramolecular vibrations. In the current work, we show Spin–Phonon couplings between IR-active phonons in a lanthanide molecular complex and Kramers doublets (from the crystal field). For the SMM Er[N(SiMe(3))(2)](3) (1, Me = methyl), the couplings are observed in the far-IR magnetospectroscopy (FIRMS) of crystals with coupling constants ≈ 2−3 cm(−1). In particular, one of the magnetic excitations couples to at least two phonon excitations. The FIRMS reveals at least three magnetic excitations (within the (4)I(15/2) ground state/manifold; hereafter, manifold) at 0 T at 104, ∼180, and 245 cm(−1), corresponding to transitions from the ground state, M(J) = ±15/2, to the first three excited states, M(J) = ±13/2, ±11/2, and ±9/2, respectively. The transition between the ground and first excited Kramers doublet in 1 is also observed in inelastic neutron scattering (INS) spectroscopy, moving to a higher energy with an increasing magnetic field. INS also gives complete phonon spectra of 1. Periodic DFT computations provide the energies of all phonon excitations, which compare well with the spectra from INS, supporting the assignment of the inter-Kramers doublet (magnetic) transitions in the spectra. The current studies unveil and measure the Spin–Phonon couplings in a typical lanthanide complex and throw light on the origin of the Spin–Phonon entanglement.

The development of precious-metal-free catalysts to promote the sustainable production of fuels and chemicals from biomass remains an important and challenging target. Here, we report the efficient hydrogenolysis of biomass-derived 5-hydroxymethylfurfural to 2,5-dimethylfuran over a unique core-shell structured catalyst Co@CoO that affords the highest productivity among all catalysts reported to date. Surprisingly, we found that the catalytically active sites reside on the shell of CoO with oxygen vacancies rather than the metallic Co. The combination of various spectroscopic experiments and computational modelling reveals that the CoO shell incorporating oxygen vacancies drives the heterolytic and homolytic cleavage of dihydrogen to yield active Hδ- species, resulting in the exceptional catalytic activity. Co@CoO also exhibits excellent activity toward the direct hydrodeoxygenation of lignin model compounds. This study unlocks, for the first time, the potential of metal-oxide catalysts for the production of renewable biomass-derived fuels.

Phonons are fundamental to understanding the dynamical and thermal properties of materials. However, first-principles phonon calculations are usually limited to moderate-size systems due to their high computational requirements. We implemented the finite displacement method (FDM) in the highly parallel real-space multigrid (RMG) suite of codes to study phonon properties. RMG scales from desktops to clusters and supercomputers containing thousands of nodes, fully supports graphics processing units (GPUs), including multiple GPUs per node, and is very suitable for large-scale electronic structure calculations. It is used as the core computational kernel to calculate the force constants matrix with FDM. By comparing with other widely used density functional theory packages and experimental data from inelastic neutron scattering, we demonstrate that RMG is very accurate in calculating forces at small displacements from equilibrium positions. The calculated phonon band structures and vibrational spectra for a variety of different systems are in very good agreement with plane-wave-based density functional theory codes, Quantum ESPRESSO, CASTEP and VASP, and these results have been validated comparing with inelastic neutron scattering experimental data measured at the VISION spectrometer at the Spallation Neutron Source.

The (meta)stability of low water activity sodium hydroxide/aluminate (Na+OH-/Al(OH)4-) electrolytes dictates kinetics in the Bayer process for aluminum refining and high-level nuclear waste processing. We utilized quasi-elastic neutron scattering (QENS) and proton nuclear magnetic resonance spectroscopy (1H NMR) in extremely concentrated sodium aluminate solutions to investigate the picosecond (ps) to microsecond (ms) timescale motions of H-bearing species (Al(OH)4- monomers/clusters, OH- and H2O). In the QENS data, in contrast to typical liquids, no short-time translational diffusion was observed at 293 K, but two types of localized motions were found: (i) local backbone tumbling or a formation of large hydrated ion clusters on the order of 40-60 ps; and (ii) much slower, complex, and collective dynamics of the ensemble of H-bearing species on the order of 350-750 ps. Variable temperature, pulsed field gradient, diffusion-ordered 1H NMR was used to determine the ensemble translational motion along with relaxometry to calculate rotational correlation coefficients. The ensemble rotational correlation times were on the order of 184-300 ps from 1H NMR, which is consistent with the timescale of the QENS components. Complementary molecular dynamics simulation of NaOH solutions exhibit extensive ion networks potentially responsible for the observed dynamical coupling of water with the motion of large hydrated ion clusters. Understanding these collective motions will aid in predicting the behavior of complex solutions during aluminum production and during nuclear waste processing.

Stability and response of supramolecular forms is important to many areas in materials science, and contributions from vibrations can be crucial. We have collected the first spectra of organic molecular crystals and polymorphic cocrystals using the next-generation, high-signal VISION spectrometer in the far-infrared (FIR) and mid-infrared (MIR) range. Unambiguously different spectral signatures were found for carbamazepine and two polymorphs of the carbamazepine-saccharin cocrystal, including numerous modes undetectable with optical methods. For FIR-range frequencies, in addition to correct calculation of peak positions, accurate line-shape features were reproducible by simulation using ab initio vibrational calculations. High confidence spectral assignments and thermochemical information for this region are thus expected, and a benchmark for vibrational ab initio calculations is provided, creating a significant addition to methods used in investigation and design of organic materials.

Quaternary clathrate-I phases with an overall composition of Ba8M16+yP30-y (M = Cu,Zn) exhibit complex structural chemistry. Characterization of the electronic structures and chemical bonding using quantum-chemical calculations and 31P solid state NMR spectroscopy demonstrated that the Cu–Zn–P framework is flexible and able to accommodate up to six Zn atoms per formula unit via bonding rearrangements, such as partial Zn/P substitution and the formation of Cu–Zn bonds. Such perturbations of the framework’s bonding affect the thermal and charge transport properties. The overall thermoelectric figure-of-merit, ZT, of Ba8Cu14Zn2P30 is 0.62 at 800 K, which is 9 times higher than the thermoelectric performance of the ternary parent phase Ba8Cu16P30. Through a combination of inelastic neutron scattering and single crystal X-ray diffraction experiments at 10 K, low-energy rattling of the Ba guest atoms inside the large tetrakaidecahedral cages are shown to be the reason for the low thermal conductivities observed...

A complex hydride (LaMg2NiH7) composed of La3+, two Mg2+, [NiH4]4– with a covalently bonded hydrogen, and three H– was formed from an intermetallic LaMg2Ni via an intermediate phase (LaMg2NiH4.6) composed of La, Mg, NiH2, NiH3 units, and H atoms at tetrahedral sites. The NiH2 and NiH3 units in LaMg2NiH4.6 were reported as precursors for [NiH4]4– in LaMg2NiH7 [Miwa et al. J. Phys. Chem. C 2016, 120, 5926–5931]. To further understand the hydrogen states in the precursors (the NiH2 and NiH3 units) and H atoms at the tetrahedral sites in the intermediate phase, LaMg2NiH4.6, we observed the hydrogen vibrations in LaMg2NiH4.6 and LaMg2NiH7 by using inelastic neutron scattering. A comparison of the hydrogen vibrations of the NiH2 and NiH3 units with that of [NiH4]4– shows that the librational modes of the NiH2 and NiH3 units were nonexistent; librational modes are characteristic modes for complex anions, such as [NiH4]4–. Furthermore, the hydrogen vibrations for the H atoms in the tetrahedral sites showed a narr...

Hydrogen gas is formed when Mg corrodes in water; however, the manner and extent to which the hydrogen may also enter the Mg metal is poorly understood. Such knowledge is critical as stress corrosion cracking (SCC)/embrittlement phenomena limit many otherwise promising structural and functional uses of Mg. Here, we report via D2O/D isotopic tracer and H2O exposures with characterization by secondary ion mass spectrometry, inelastic neutron scattering vibrational spectrometry, electron microscopy, and atom probe tomography techniques direct evidence that hydrogen rapidly penetrated tens of micrometers into Mg metal after only 4 h of exposure to water at room temperature. Further, technologically important microalloying additions of

Here we report direct physical evidence that confinement of molecular hydrogen (H2) in an optimized nanoporous carbon results in accumulation of hydrogen with characteristics commensurate with solid H2 at temperatures up to 67 K above the liquid-vapour critical temperature of bulk H2. This extreme densification is attributed to confinement of H2 molecules in the optimally-sized micropores, and occurs at pressures as low as 0.02 MPa. The quantities of contained, solid-like H2 increased with pressure and were directly evaluated using in-situ inelastic neutron scattering and confirmed by analysis of gas sorption isotherms. The demonstration of the existence of solid-like hydrogen challenges the existing assumption that supercritical hydrogen confined in nanopores has an upper limit of liquid H2 density. Thus, this insight offers opportunities for the development of more accurate models for the evaluation and design of nanoporous materials for high capacity adsorptive hydrogen storage.

We address the reactivity of lithiated graphite–anode material for Li-ion batteries with standard organic solvents used in batteries (ethylene carbonate and dimethyl carbonate) by following changes in neutron scattering signals. The reaction produces a nanosized layer, the solid-electrolyte interphase (SEI), on the graphite particles. We probe the structure and chemistry of the SEI using small-angle neutron scattering (SANS) and inelastic neutron scattering. The SANS results show that the SEI fills 20–30 nm sized pores, and inelastic scattering experiments with H/D substitution show that this “chemical” SEI is primarily organic in nature; that is, it contains a large amount of hydrogen. The graphite–SEI particles show surface fractal scattering characteristic of a rough particle–void interface and are interconnected. The observed changes in the SEI structure and composition provide new insight into SEI formation. The chemically formed SEI is complementary and simpler in composition to the electrochemicall...

Polyoligosilsesquioxanes (POSS) are a large family of Si–O cage molecules that have diameters of 1–2 nm and can be viewed as perfectly monodisperse silica nanoparticles. POSS can be synthesized wit...

This study aims at an investigation of the impurity gases emitted during the decomposition of borohydrides. For this we have set up a quantitative gas analysis based on a combination of FTIR spectroscopy and gravimetry. We show that the emission of various intermediates, in particular diborane, depends sensitively on the reaction conditions, including gas mean free path lengths, hydrogen backpressure, and sample pretreatment. Adduct-free Mg(BH 4)2 and LiBH4 emit diborane only at the impurity level, while for LiZn2(BH4)5 diborane is the main decomposition product. The decomposition reaction of LiZn 2(BH4)5 proceeds via a collision-induced dissociation of Zn(BH4)2 in Ar at ambient pressures. Various additives were tested aiming at catalyzing the decomposition of the desorbed diborane. © 2011 American Chemical Society.

Practical methods for hydrogen storage are still a major bottleneck in the realization of an energy economy based on hydrogen as an energy carrier.(1) Surface adsorption within crystalline, nanoporous, metal−organic frameworks (MOFs) provides a promising storage method that relies on sufficiently strong adsorption interactions for a large fraction of the storage capacity. Only few MOF structures were studied up to date using neutron diffraction to resolve the adsorption sites.(2-5) Here we use in situ neutron diffraction to characterize hydrogen (deuterium) adsorption sites in the MOF Cr MIL-53. The strongest adsorption interactions are present at three different sites where the hydrogen touches nearby organic linkers from two directions. Perhaps surprisingly, there is no strong direct interaction with the Cr−O cluster. Large breathing modes of the crystalline lattice are observed upon loading hydrogen reversibly to an equivalent of 5.5 wt %. Such breathing modes are known to occur for polar solvents like...

Raman spectra of Mg(BH(4))(2) have been measured in an extensive temperature range, from 15 to 473 K. Taking into account the high temperature conversion from the alpha to the beta phase, we have observed evident signatures of this phase transition and determined the Raman vibrational spectrum of each phase. The neutron scattering spectra of the beta phase sample were also recorded. The present experimental results have been compared to the density functional theory calculations available in the literature, and a substantial agreement has been found.

Employing femtosecond IR pump-probe and 2D spectroscopy, we measure the vibrational dynamics of LiBH(4) and several of its deuterium isotopomers. We find that the vibrational lifetime of various BH and BD stretching modes uniformly is approximately 1.5 ps for all BH(4-x)D(x)(-) units (0or=xor=4). Subsequently, vibrational energy cascades down through BH and BD bending, facilitated by a strong Fermi resonance, into external (librational and translational) modes with a 3 ps time constant. Final thermalization of the energy is completed in about 100 ps. The vibrational spectra are purely homogeneously broadened indicating low inhomogeneity due to static disorder. We furthermore measured the anharmonic constants of various modes, which sets the benchmark for future ab initio calculations, and completed the first FTIR assignment of the stretching vibrations for the five BH(4-x)D(x)(-) units.

The metal-organic framework, MIL-53, can have a structural transition from an open-pored to a closed-pored structure by adsorbing different guest molecules. The aid of guest molecules is believed to be necessary to initiate this "breathing" effect. Using both neutron powder diffraction and inelastic neutron scattering techniques, we find that MIL-53 exhibits a reversible structural transition between an open-pored and a closed-pored structure as a function of temperature without the presence of any guest molecules. Surprisingly, this structural transition shows a significant temperature hysteresis: the transition from the open-pored to closed-pored structure occurs at approximately 125 to 150 K, while the transition from the closed-pored to open-pored structure occurs around 325 to 375 K. To our knowledge, this is first observation of such a large temperature hysteresis of a structural transition in metal-organic frameworks. We also note that the transition from the open to closed structure at low temperature shows very slow kinetics. An ab initio computer simulation is employed to investigate the possible mechanism of the transition.

Differential scanning calorimetry of the hydrated, microporous aluminum phosphate AlPO-14 shows two distinct water losses between room temperature and 120 degrees C, indicating the presence of two types of water in the solid. Multiple-quantum magic angle spinning (MQMAS) (27)Al NMR shows that, while in dehydrated AlPO-14 all aluminum is found in tetrahedral sites, on hydration a significant proportion of the aluminum increases its coordination number to 6. This accounts for the presence of tightly bound water. The first detailed incoherent inelastic neutron scattering (IINS) studies of such a system give a spectrum with distinct and sharp librational bands for bound water, significantly different than seen in ice Ih. Using these data, and by consideration of the crystal structure of dehydrated AlPO-14, we propose a model for the hydrated material in which the tightly bound water bridges pairs of Lewis acidic framework aluminums in a dense region of the structure, while loosely bound water resides in the pores of the solid. Further IINS measurements using a high-incident neutron energy provide data that are in agreement with our model. We can detect two O-H stretching modes for bound water in hydrated AlPO-14, consistent with the model of two types of water present in the material, with the loosely bound water connected to neighboring water molecules by intermolecular hydrogen bonds.

Hydrogen spillover on carbon-supported precious metal catalysts has been investigated with inelastic neutron scattering (INS) spectroscopy. The aim, which was fully realized, was to identify spillover hydrogen on the carbon support. The inelastic neutron scattering spectra of Pt/C, Ru/C, and PtRu/C fuel cell catalysts dosed with hydrogen were determined in two sets of experiments: with the catalyst in the neutron beam and, using an annular cell, with carbon in the beam and catalyst pellets at the edge of the cell excluded from the beam. The vibrational modes observed in the INS spectra were assigned with reference to the INS of a polycyclic aromatic hydrocarbon, coronene, taken as a molecular model of a graphite layer, and with the aid of computational modeling. Two forms of spillover hydrogen were identified: H at edge sites of a graphite layer (formed after ambient dissociative chemisorption of H-2), and a weakly bound layer of mobile H atoms (formed by surface diffusion of H atoms after dissociative chernisorption of H-2 at 500 K). The INS spectra exhibited characteristic riding modes of H on carbon and on Pt or Ru. In these riding modes H atoms move in phase with vibrations of the carbon and metal lattices. The lattice modes are amplified by neutron scattering from the H atoms attached to lattice atoms. Uptake of hydrogen, and spillover, was greater for the Ru containing catalysts than for the Pt/C catalyst. The INS experiments have thus directly demonstrated H spillover to the carbon support of these metal catalysts.

We have carried out a comprehensive characterization of the structure and dynamics of maleic anhydride using experimental (single-crystal neutron diffraction, infrared, Raman and inelastic neutron scattering (INS) spectroscopies) and computational methods (AM1 and two levels of density functional theory). The structure is largely in agreement with previous work, although with more accurate atomic positions. However, the report of an unusually short CC bond length is not supported by this work. The combination of ab initio results and INS spectra has confirmed the assignments of the internal modes. In addition, the complete lattice mode region is observed and assigned for the first time. Force fields derived by empirical means and from the ab initio data have been obtained and show differences, although both accurately predict the INS spectrum.