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α-Synuclein (αSyn) is an intrinsically disordered protein that can form amyloid fibrils. Fibrils of αSyn are implicated with the pathogenesis of Parkinson's disease and other synucleinopathies. Elucidating the mechanism of fibril formation of αSyn is therefore important for understanding the mechanism of the pathogenesis of these diseases. Fibril formation of αSyn is sensitive to solution conditions, suggesting that fibril formation of αSyn arises from the changes in its inherent physico-chemical properties, particularly its dynamic properties because intrinsically disordered proteins such as αSyn utilize their inherent flexibility to function. Characterizing these properties under various conditions should provide insights into the mechanism of fibril formation. Here, using the quasielastic neutron scattering and small-angle x-ray scattering techniques, we investigated the dynamic and structural properties of αSyn under the conditions, where mature fibrils are formed (pH 7.4 with a high salt concentration), where clumping of short fibrils occurs (pH 4.0), and where fibril formation is not completed (pH 7.4). The small-angle x-ray scattering measurements showed that the extended structures at pH 7.4 with a high salt concentration become compact at pH 4.0 and 7.4. The quasielastic neutron scattering measurements showed that both intra-molecular segmental motions and local motions such as side-chain motions are enhanced at pH 7.4 with a high salt concentration, compared to those at pH 7.4 without salt, whereas only the local motions are enhanced at pH 4.0. These results imply that fibril formation of αSyn requires not only the enhanced local motions but also the segmental motions such that proper inter-molecular interactions are possible.

"Water-in-salt" (WIS) and "water-in-bisalt" (WIBS) electrolytes have recently been developed for Li-ion batteries, combining the safety and environmental friendliness of aqueous electrolytes with a larger operating window made possible by a solid-electrolyte interphase. We report quasielastic neutron scattering (QENS) measurements on solutions of a WIS electrolyte at two concentrations, 13.9 and 21 m (molal) lithium bis(trifluoromethane)sulfonimide LiTFSI in H2O/D2O and a WIBS electrolyte at (21 m LiTFSI + 7 m lithium triflate (LiOTf)) in H2O/D2O. The data were Fourier transformed to obtain experimental intermediate scattering functions (ISFs) and compared with corresponding quantities obtained from molecular dynamics (MD) simulations. Both QENS and MD ISFs could be fitted well by a single stretched exponential function to obtain apparent translational diffusion coefficients for the water molecules. The QENS values agree well with the MD simulations for the 13.9 and 21 m solutions, but MD simulations predict a slower relaxation of water compared to QENS for the WIBS electrolyte. Comparison of the incoherent and coherent scattering reveals much faster water dynamics compared with structural relaxation of the ionic framework, consistent with the nanodomain picture where the lithium diffusion occurs through the tortuous water domain around the slower relaxing ionic matrix, leading to highly non-Gaussian water motion.

Quasielastic neutron scattering is applied to analyse the atomic scale hydrogen transport processes occurring within the crystal lattices of hydrous minerals. Two types of transport processes were observed in Mg(OH)2, which has a prototypical layered hydrogen lattice structure., It is demonstrated that quasielastic neutron scattering is a novel and effective method to analyse atomic scale hydrogen transport processes occurring within a mineral crystal lattice. The method was previously characterized as sensitive for analysing the transport frequency and distance of highly diffusive hydrogen atoms or water molecules in condensed matter. Here are shown the results of its application to analyse the transport of much slower hydrogen atoms which are bonded into a crystal lattice as hydroxyls. Two types of hydrogen transport process were observed in brucite, Mg(OH)2: a jump within a single two-dimensional layer of the hydrogen lattice and a jump into the next nearest layer of it. These transport processes observed within the prototypical structure of brucite have direct implications for hydrogen transport phenomena occurring within various types of oxides and minerals having layered structures.

The dynamics of methanol confined in highly cross-linked phenolic resins was investigated using incoherent quasielastic neutron scattering (QENS) and atomistic molecular dynamics (MD) simulations. ...

Nano-confined water (a water pocket) was spontaneously formed using an ionic liquid (IL), 1-butyl-3-methylimidazolium nitrate ([C4mim][NO3]), in [C4mim][NO3]-H2O and [C4mim][NO3]-D2O mixtures. The static average size of the water pocket in [C4mim][NO3]-80 mol% D2O has been estimated to be around 20 A, determined via small-angle neutron scattering measurements (Abe et al., J. Phys. Chem. Lett., 2014, 5, 1175). In this study, the dynamics of the water pocket in the IL were directly examined using incoherent quasielastic neutron scattering. Using the H-D difference of a neutron incoherent scattering cross section, the extent of the diffusion of the water molecules in the water pocket was determined. The water pocket could be characterized due to the slow dynamics of the water compared with those of bulk water.

J-PARC, Japan Proton Accelerator Research Complex provides short pulse proton beam at a repetition rate 25Hz and the maximum power is expected to be 1MW. Materials and Life Science Experimental Facility (MLF) has 23 neutron beam ports and 21 instruments have already been operated or under construction/commissioning. There are 6 inelastic/quasi-elastic neutron scattering spectrometers and the complementary use of these spectrometers will open new insight for life science.This article is part of a Special Issue entitled “Science for Life” Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.

Ionic liquids (ILs) are potential candidates for new antimicrobials due to their tunable antibacterial and antifungal properties that are required to keep pace with the growing challenge of bacterial resistance. To a great extent their antimicrobial actions are related to the interactions of ILs with cell membranes. Here, we report the effects of ILs on the nanoscopic dynamics and phase behaviour of a dimyristoylphosphatidylcholine (DMPC) membrane, a model cell membrane, as studied using neutron scattering techniques. Two prototypical imidazolium-based ILs 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM[BF4]) and 1-decyl-3-methylimidazolium tetrafluoroborate (DMIM[BF4]), which differ only in terms of the alkyl chain length of cations, have been used for the present study. Fixed Elastic Window Scan (FEWS) shows that the incorporation of ILs affects the phase behaviour of the phospholipid membrane significantly and the transition from a solid gel to a fluid phase shifts to lower temperature. This is found to be consistent with our differential scanning calorimetry measurements. DMIM[BF4], which has a longer alkyl chain cation, affects the phase behaviour more strongly in comparison to BMIM[BF4]. The pressure-area isotherms of the DMPC monolayer measured at the air-water interface show that in the presence of ILs, isotherms shift towards higher area-per lipid molecule. DMIM[BF4] is found to shift the isotherm to a greater extent compared to BMIM[BF4]. Quasielastic neutron scattering (QENS) data show that both ILs act as a plasticizer, which enhances the fluidity of the membrane. DMIM[BF4] is found to be a stronger plasticizing agent in comparison to BMIM[BF4] that has a cation with a shorter alkyl chain. The incorporation of DMIM[BF4] enhances not only the long range lateral motion but also the localised internal motion of the lipids. On the other hand, BMIM[BF4] acts weakly in comparison to DMIM[BF4] and mainly alters the localised internal motion of the lipids. Any subtle change in the dynamical properties of the membrane can profoundly affect the stability of the cell. Hence, the dominant effect of the IL with the longer chain length on the dynamics of the phospholipid membrane might be correlated with its cytotoxic activity. QENS data analysis has provided a quantitative description of the effects of the two imidazolium-based ILs on the dynamical and phase behaviour of the model cell membrane, which is essential for a detailed understanding of their action mechanism.

Characterization of the dynamics of disordered polypeptide chains is required to elucidate the behavior of intrinsically disordered proteins and proteins under non-native states related to the folding process. Here we develop a method using quasielastic neutron scattering, combined with small-angle X-ray scattering and dynamic light scattering, to evaluate segmental motions of proteins as well as diffusion of the entire molecules and local side-chain motions. We apply this method to RNase A under the unfolded and molten-globule (MG) states. The diffusion coefficients arising from the segmental motions are evaluated and found to be different between the unfolded and MG states. The values obtained here are consistent with those obtained using the fluorescence-based techniques. These results demonstrate not only feasibility of this method but also usefulness to characterize the behavior of proteins under various disordered states.

We studied the dynamics of zinc diacrylate (ZDA) reinforced polybutadiene rubber (BR) (ZDA/BR) using the quasielastic neutron scattering technique to determine the effect of concentration of ZDA on polymer dynamics. First, we evaluated the temperature dependence of mean square displacements (〈u2〉) for ZDA/BR with different ZDA volume fractions. 〈u2〉 increased with temperature below 170 K, and we observed no significant ZDA volume fraction dependence. However, it increased more steeply above 170 K, and the value of 〈u2〉 was smaller for the samples with increasing ZDA fraction. To elucidate the origin of the decrease in 〈u2〉 with increasing ZDA content, dynamic scattering laws (S(Q,ω)) were analyzed. An increase in the elastic component, an increase in the mean relaxation time, and a broadening of distribution of relaxation time were observed with the increasing volume fraction of ZDA. In addition, the ZDA volume fraction dependence of the elastic component roughly corresponded to that of elastic modulus, indicating that the elastic component is related to its mechanical strength. Referring to the previously reported static structure of the present ZDA/BR system, a model for the heterogeneous BR dynamics was proposed. This model assumes the coexistence of immobile, mobile, and interfacial constrained mobile regions. It was found to be appropriate for the explanation of the observed dynamics. We proposed that a network-like structure of the BR having a high crosslinking density around ZDA aggregates is mainly responsible for the high elastic modulus of ZDA/BR.

Hemoglobin, the vital O2 carrier in red blood cells, has long served as a classic example of an allosteric protein. Although high-resolution X-ray structural models are currently available for both the deoxy tense (T) and fully liganded relaxed (R) states of hemoglobin, much less is known about their dynamics, especially on the picosecond to subnanosecond time scales. Here, we investigate the picosecond dynamics of the deoxy and CO forms of human hemoglobin using quasielastic neutron scattering under near physiological conditions in order to extract the dynamics changes upon ligation. From the analysis of the global motions, we found that whereas the apparent diffusion coefficients of the deoxy form can be described by assuming translational and rotational diffusion of a rigid body, those of the CO form need to involve an additional contribution of internal large-scale motions. We also found that the local dynamics in the deoxy and CO forms are very similar in amplitude but are slightly lower in frequency...

Troponin (Tn), consisting of three subunits (TnC, TnI, and TnT), regulates cardiac muscle contraction in a Ca2+-dependent manner. Various point mutations of human cardiac Tn are known to cause familial hypertrophic cardiomyopathy due to aberration of the regulatory function. In this study, we investigated the effects of one of these mutations, K247R of TnT, on the picosecond dynamics of the Tn core domain (Tn-CD), consisting of TnC, TnI and TnT2 (183–288 residues of TnT), by carrying out the quasielastic neutron scattering measurements on the reconstituted Tn-CD containing either the wild-type TnT2 (wtTn-CD) or the mutant TnT2 (K247R-Tn-CD) in the absence and presence of Ca2+. It was found that Ca2+-binding to the wtTn-CD decreases the residence time of atomic motions in the Tn-CD with slight changes in amplitudes, suggesting that the regulatory function mainly requires modulation of frequency of atomic motions. On the other hand, the K247R-Tn-CD shows different dynamic behavior from that of the wtTn-CD both in the absence and presence of Ca2+. In particular, the K247R-Tn-CD exhibits a larger amplitude than the wtTn-CD in the presence of Ca2+, suggesting that the mutant can explore larger conformational space than the wild-type. This increased flexibility should be relevant to the functional aberration of this mutant.

From the quasi-elastic neutron scattering experiment, dynamic structure factors, S(Q, E) were obtained at both 1000°C and 1500°C. To understand the distribution of the dynamic structure factor as a scattering low, the half-width at half-maximum (HWHM) of dynamic structure factor was determined. It is clear that the Q dependence for HWHM of S(Q, E) does not fulfil the rigorous definition on the condition of the phenomenon called the de Gennes narrowing. From the Fourier transform, the intermediate scattering function, F(Q, t), is obtained. From the result of F(Q, t), it is clear that the relaxation process of liquid germanium is different from that of simple liquid.

Alkyl-methyl-imidazolium ionic liquids CnmimX (n: alkyl-carbon number, X: anion) have short-range layer structures consisting of ionic and neutral (alkylchain) domains. To investigate the temperature dependences of the interlayer, interionic group, and inter-alkylchain correlations, we have measured the neutron diffraction (ND) of C16mimPF6, C9.5mimPF6, and C8mimPF6 in the temperature region from 4 K to 470 K. The quasielastic neutron scattering (QENS) of C16mimPF6 was also measured to study the dynamics of each correlation. C16mimPF6 shows a first-order transition between the liquid (L) and liquid crystalline (LC) phases at Tc = 394 K. C8mimPF6 exhibits a glass transition at Tg = 200 K. C9.5mimPF6, which is a 1:3 mixture between C8mimPF6 and C10mimPF6, has both transitions at Tc = 225 K and Tg = 203 K. In the ND experiments, all samples exhibit three peaks corresponding to the correlations mentioned above. The widths of the interlayer peak at ca. 0.2 A−1 changed drastically at the L-LC transitions, while the interionic peaks at ca. 1 A−1 exhibited a small jump at Tc. The peak position and area of the three peaks did not change much at the transition. The structural changes were minimal at Tg. The QENS experiments demonstrated that the relaxation time of the interlayer motion increased tenfold at Tc, while those of other motions were monotonous in the whole temperature region. The structural and dynamical changes mentioned above are characteristic of the L-LC transition in imidazolium-based ionic liquids.Alkyl-methyl-imidazolium ionic liquids CnmimX (n: alkyl-carbon number, X: anion) have short-range layer structures consisting of ionic and neutral (alkylchain) domains. To investigate the temperature dependences of the interlayer, interionic group, and inter-alkylchain correlations, we have measured the neutron diffraction (ND) of C16mimPF6, C9.5mimPF6, and C8mimPF6 in the temperature region from 4 K to 470 K. The quasielastic neutron scattering (QENS) of C16mimPF6 was also measured to study the dynamics of each correlation. C16mimPF6 shows a first-order transition between the liquid (L) and liquid crystalline (LC) phases at Tc = 394 K. C8mimPF6 exhibits a glass transition at Tg = 200 K. C9.5mimPF6, which is a 1:3 mixture between C8mimPF6 and C10mimPF6, has both transitions at Tc = 225 K and Tg = 203 K. In the ND experiments, all samples exhibit three peaks corresponding to the correlations mentioned above. The widths of the interlayer peak at ca. 0.2 A−1 changed drastically at the L-LC transitions, while...

Designing the next generation of lithium ion batteries requires fundamental information that surprisingly often is still unknown---for example, details of how ions actually move through a working device. The authors use state-of-the-art quasielastic neutron scattering to directly monitor the fast diffusion of Li${}^{+}$ in a promising solid electrolyte. Here the ions migrate between stable regions within a jump length $llg$ = 4.3 \AA{} along conduction pathways that thread stacks of tetrahedral motifs in the crystal structure. This understanding is key to improved energy storage for applications ranging from vehicles to future smart grids.

Inelastic X-ray and neutron scattering experiments are powerful tools on studying atomic dynamics in a liquid. These are complemental technique for liquid dynamics due to their different characters. As an example of structurally disordered materials, we report the atomic dynamics on liquid Ge by means of the inelastic X-ray and neutron scattering experiments. The acoustic phonon dispersion and the quasielastic scattering spectrum due to the structural relaxations are discussed in association with the anomaly in the static structure.

Quasielastic neutron scattering measurements of liquid germanium were performed at 1000°C using the inverted geometry inelastic neutron spectrometer, LAM-40. The dynamic structure factor is obtained over a wide momentum transfer region from 0.6 to 5.1 A−1. It is found that the shoulder structure at the high-Q side of the first peak of the static structure factor originates from a distinct sub peak which can clearly be identified in S(Q,E).

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

In order to reveal the dynamical properties specific to the folded protein, inelastic neutron scattering measurements were performed for the folded and the unfolded Staphylococcal nuclease, and myoglobin at 100 K and 300 K. The observed S ( Q , ω ) at 100 K for these three were essentially identical. Protein individuality was not expressed in the low energy dynamics at low temperature. The peak position of low energy excitation showed molecular weight dependence, suggesting that the excitation is originated from modes extended over a whole molecule. The changes in dynamical properties upon folding were observed at 300 K, suggesting that anharmonic motion is essential for function.

A composite glass, CuI–Cu 2 MoO 4 , has an ionic conductivity at room temperature, corresponding to ionic liquid conductivity. Pulsed neutron scattering and XAFS measurements show that the main framework of the sample is constructed from [MoO 4 ]-tetrahedra and [MoO 6 ]-octahedra. Cu + ions in the glass are bound to 2 O atoms or 4 I atoms. he atomic motion below 20 meV in the sample measured at room temperature is close to that of the α-CuI crystalline state near its melting point. In addition to the Boson peak, above 200 K, quasielastic neutron scattering due to the local diffusion of Cu + ions is found at energies 5 meV. The long-range translational diffusion of the Cu + ions in the sample is directly demonstrated by high resolution quasielastic neutron scattering results. The broadening is less than 100 μeV. The hierarchic static and dynamic structure of the sample is shown to control the properties of the super-ionic conducting glass, CuI–Cu 2 MoO 4 .

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

Quasielastic neutron scattering experiments have been performed on the glass-forming nitrate liquid, 0.38Ca(NO3)2 · 0.62KNO3. The experiments were carried out using the medium resolution LAM-40 inverted geometry time of flight spectrometer installed at the neutron scattering facility KENS, KEK, Japan. The measured spectra consist of narrow and broad quasielastic components. The broad component of the spectra corresponds to the fast intra-ionic motions in a nitrate ion. From the momentum dependence of the integrated intensity for this component, it is found that the motion of the nitrate ions in this liquid is mainly the librational one around the C3 axis of the ion. According to the momentum dependence of the linewidth, this motion is expected to be a jump-diffusional motion. These results suggest that the intra-molecular motion of the nitrate ions in the liquid is strongly restricted by the surrounding cations.

α-synuclein (αSyn) is a protein consisting of 140 amino acid residues and is abundant in the presynaptic nerve terminals in the brain. Although its precise function is unknown, the filamentous aggregates (amyloid fibrils) of αSyn have been shown to be involved in the pathogenesis of Parkinson's disease, which is a progressive neurodegenerative disorder. To understand the pathogenesis mechanism of this disease, the mechanism of the amyloid fibril formation of αSyn must be elucidated. Purified αSyn from bacterial expression is monomeric but intrinsically disordered in solution and forms amyloid fibrils under various conditions. As a first step toward elucidating the mechanism of the fibril formation of αSyn, we investigated dynamical behavior of the purified αSyn in the monomeric state and the fibril state using quasielastic neutron scattering (QENS). We prepared the solution sample of 9.5 mg/ml purified αSyn, and that of 46 mg/ml αSyn in the fibril state, both at pD 7.4 in D2O. The QENS experiments on these samples were performed using the near-backscattering spectrometer, BL02 (DNA), at the Materials and Life Science Facility at the Japan Accelerator Research Complex, Japan. Analysis of the QENS spectra obtained shows that diffusive global motions are observed in the monomeric state but largely suppressed in the fibril state. However, the amplitude of the side chain motion is shown to be larger in the fibril state than in the monomeric state. This implies that significant solvent space exists within the fibrils, which is attributed to the αSyn molecules within the fibrils having a distribution of conformations. The larger amplitude of the side chain motion in the fibril state than in the monomeric state implies that the fibril state is entropically favorable.

We have carried out quasielastic neutron scattering measurements on liquid tellurium (l-Te) at 460°C, and inelastic neutron scattering measurements on trigonal tellurium (t-Te) at 400°C, supercooled l-Te at 400°C and l-Te at 467°C. The quasielastic scattering peak is comparatively narrow at momentum transfer Q =2.0 A -1 where the first peak of the static structure factor is seen. The vibrational density of states (V-DOS) of supercooled l-Te has a three-band structure similar to that of t-Te, indicating that the chain structure is preserved in the liquid state. The V-DOS of l-Te changes remarkably with temperature, which strongly demonstrates the modification of chain structure in the liquid state.

We constructed a crystal analyzer type inelastic scattering neutron spectrometer LAM-D at the KENS spallation thermal neutron source in the National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. This spectrometer can cover the energy transfer range up to 300 meV with a resolution ΔϵE1 of less than 6%. The basic principle of LAM-D is the same as the quasi-elastic scattering spectrometers LAM-40 and LAM-80 at KENS so that the combination of the three spectrometers is a very powerful tool for studies of molecular motions in condensed matters in the energy range of 1 μeV to 300 meV.

Quasielastic neutron scattering experiments have been performed on molten RbNO 3 , The quasielastic spectra are composed of narrow and broad coherent components. The narrow component is assigned to the translational motion due to the diffusion of the center of gravity of each ion. The broad component corresponds to fast intra-ionic motions within the nitrate ion. From the momentum dependence of the broad component, it is concluded that the nitrate ion in molten RbNO 3 is mainly subjected to a rotational vibration centered around the C 3 axis and that the form of the nitrate motion around C 3 axis does not change with increasing temperature.

We have recently developed a high resolution quasielastic neutron scattering spectrometer LAM-80ET by applying mica crystals as analyzers and achieved a resolution of Δ e =1.3 µeV using the 002 reflection. Single chain dynamics of polyethylene has been investigated below and above the melting temperature T m (=135°C) to show the feasibility of the mica 002 reflection as the analyzer. It was found that elastic scattering intensity from polyethylene decreases very steeply around the T m . Quasielastic broadening in the spectrum at Q =0.082 A -1 is observed only above 210°C, which is 75°C higher than the T m . From the analysis of the spectra by a curve-fitting method, the width of the quasielastic component was evaluated to be 1.8 µeV at 250°C and the activation energy of the width to be 34 kJ/mol.

Proton diffusion was observed in Y-doped SrZrO 3 ceramics above 500°C by quasielastic neutron scattering. The line width of the quasielastic component varies with energy transfer Q and temperature. The temperature dependence is well elucidated by the thermal activation-type proton migration with activation energy of 0.2 eV. The observed hopping distance was 1.7 A, which is comparable to one of the distances between two proton sites.

Quasielastic neutron scattering shows that the dynamical structure factor of 0.80RbNO3−0.20Sr(NO3)2 melt is composed of two components of narrow and broad spectrum. The narrow component is assigned to the slow mode inter-ionic motions of the ionic center of gravity, which are almost frozen at the glass transition temperature. The broad component corresponds to the fast intra-ionic motions in a NO3− anion of which amplitudes are vanishing with approaching to the glass transition temperature.

We studied the low-energy excitations in the meV region as well as the picosecond fast process in polystyrene thin supported films using inelastic and quasielastic neutron scattering in a temperature range from $11\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}430\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, covering the bulk glass transition temperature ${T}_{\mathrm{g}}$. It was found that the mean square displacement $⟨{u}^{2}⟩$ decreased with the film thickness below and above the glass transition temperature ${T}_{\mathrm{g}}$, suggesting that the hardening occurs with decreasing the film thickness. Corresponding to the decrease in $⟨{u}^{2}⟩$, it was also found that the density of phonon states $G(\ensuremath{\omega})$ decreased with film thickness. This decrease occurs mainly in the Debye mode while the contribution of the boson peak mode also decreases with the film thickness without changing the boson peak energy. As for the fast process, which appeared above at about $150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ as a quasielastic scattering, the fraction ${A}_{\mathit{\text{fast}}}(Q)$ decreased with the film thickness in a similar manner with the boson peak without changing the relaxation rate, suggesting a common origin for the boson peak and the fast process. These observations showing the hardening were well explained by assuming a hard dense layer at the interface, where the numbers of the boson peak mode as well as the fast process are less than the bulk state.

The results of inelastic neutron scattering measurements for Ag2GeSe3 are reported in association with a low energy excitation and Ag diffusion. A low energy excitation peaked at 2.4 meV and underling tail below 10meV are observed from 120K to 300K. Glass structure based on Ge-Se covalent bond persists in this material, that is confirmed by observation of stretching and bending modes of Ge-Se bond.