Position Of First Sharp Diffraction Peak Research Articles

The boson peak and the first sharp diffraction peak in (As2S3)x(GeS2)1–x glasses

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant.

Structural correlation of GeTeSeGa system by XRD and far-infrared spectroscopy

The structural properties of quaternary Ge10Te80Se10-xGax (x = 0 to 10) glassy alloy have been studied with XRD (X-ray diffraction) and FTIR (Fourier transform infrared) spectroscopy. The position of FSDP (first sharp diffraction peak) (2θ) and its FWHM (full width half maxima) have been utilized to estimate the local structure parameters of FSDP like repeating distance y and structural correlation length (L). The far-infrared (IR) transmission spectra of Ge10Te80Se10-xGax (x = 0, 2, 4, 6, 8, 10) have been analysed in the range 30–300 cm−1 to study the formation of bonds using chain crossing model, random covalent network model and chemical bond approach. The theoretical calculations have been executed for bond energies, force constants, wave number, etc., for probable bonds, and the results justify the experimental values. The present study contributes to the understanding of the composition-dependent structural property relationship of chalcogenide glasses.

Effect of high‐energy mechanical milling on the medium‐range ordering in glassy As‐Se

AbstractEffect of high‐energy mechanical milling on glassy AsxSe100 − x (5 ≤ x ≤ 75) is recognized with X‐ray powder diffraction analysis applied to their diffuse halos ascribed to intermediate—and extended‐range structural ordering, which are revealed respectively in the first sharp diffraction peak (FSDP) and principal diffraction peak (PDP). Straightforward interpretation of the results is developed within modified microcrystalline approach, treating diffuse halos as superposition of broadened Bragg‐diffraction reflexes from remnants of inter‐planar correlations, supplemented by inter‐atomic Ehrenfest‐diffraction reflexes from most prominent inter‐atomic and inter‐molecular correlations between cage‐like molecules (such As4Se4 and/or As4Se3). Milling is shown to be ineffective in glassy arsenoselenides near Se (x < 20), while causing increase in the FSDP width for glasses with 20 ≤ x ≤ 40 due to destroyed inter‐planar ordering. Remnants of cage‐like molecules in over‐stoichiometric As‐rich AsxSe100 − x glasses (40 ≤ x ≤ 75) disappear under milling, promoting formation of higher polymerized structural network. This milling‐driven reamorphization results in a drastic increase in the FSDP position and fragmentation impact on the correlation length of the FSDP‐responsible entities. Breakdown in intermediate‐range ordering in these glasses is accompanied by changes in their extended‐range ordering revealed in high‐angular shift and broadening of the PDP. This effect is concomitant with the disappearance of distant inter‐atomic correlations between quasi‐crystalline planes in the milled arsenoselenide glasses at a cost of prolonged correlations dominating in their extended‐range ordering.

Critical remark on the FSDP-related correlations in chalcogenide glasses as treated in the paper [Alekberov RI, Isayev AI, Mekhtiyeva SI, Fábián M. Local structures and optical properties of As-Se-Te(S) chalcogenide glasses. Phys B: Condens Matter 2018; 550: 367–375

Abstract In the paper [Phys. B 550 (2018) 367–375], Alekberov, Isayev, Mekhtiyeva and Fabian have performed very erroneous calculation on diameter of voids responsible for the first sharp diffraction peak (FSDP) in neutron diffraction patterns of As2Se3-based glasses. The authors used wrong relation for the FSDP position taken from entirely speculative assertion presented by Kavetskyy in [Semicond. Phys. Quantum Electron. Optoelectron. 16 (2013) 136–139], assuming unreasonable equivalence between chemistry of chalcogenide glasses and typical polymers. In this communication, the deep reason for this incorrectness was disclosed, and alternative variant to estimate diameters of interstitial voids responsible for the FSDP in As2Se3-based glasses was presented.

Medium-range structural changes in glassy As2S3 driven by high-energy mechanical milling

Effect of high-energy dry mechanical milling on medium-range order structure in glassy arsenic sulfide g-As2S3 was studied employing the X-ray powder diffraction (XRPD) analysis. The results were treated in terms of model assuming appearance of diffuse halo in the XRPD patterns of g-As2S3 known as the FSDP (the first sharp diffraction peak) due to remnants of inter-planar quasi-crystalline correlations with Bragg diffraction spacing approaching ~5.1 Å, supplemented by the post-FSDP halo at ~1.5 Å−1 originated from inter-atomic cation-cation correlations. Thermodynamically stabilized balance in network-forming entities in glass structure was shown to be essentially disturbed under milling, providing an evidence on a variety of defective states with unfavorable potential energies. The inter-planar correlations contributing to the FSDP were essentially disturbed under milling making the correlated distances between atomic pairs belonging to neighboring planes more prominent, like it was detected in chalcogenide glasses under applied hydrostatic pressure. The impact of milling-driven fragmentation on the correlation lengths of quasi-crystalline remnants was confirmed by slight decrease in the FSDP position and, in contrast, noticeable broadening in its width. The non-elementary nature of this peak-halo due to post-FSDP hump became more prominent after high-energy milling. Comparative study of milling-derived g-As45S55 and As50S50 mechanically treated under similar conditions confirmed unique compositional FSDP parameterization in binary g-As-S system.

Pressure-induced structural changes in titanophosphate glasses studied by neutron and X-ray total scattering analyses

In this paper, the densification mechanism of two titanophosphate glasses (binary 73TiO2-27P2O5 and ternary 68TiO2-5Al2O3-27P2O5) is investigated. The glasses are densified by isostatic N2-mediated pressure treatment at elevated temperature and the pressure-induced structural changes are studied by neutron and X-ray total scattering analyses. The medium range structure change is revealed from the change in the first sharp diffraction peak (FSDP), where the density increase by pressurization is correlated with the decreased medium range repeating spacing calculated from the position of FSDP. The hot compression treatment also increases the medium range order, as shown by the increased correlation length calculated from the width of FSDP. The short range structure changes are examined by separating PO and TiO pair distribution functions (PDF) using differential neutron and X-ray PDFs. Pressurization is also found to increase the coordination number of Ti, as previously observed for other network formers in densified glasses.

Contrasting sound velocity and intermediate-range structural order between polymerized and depolymerized silicate glasses under pressure

X-ray diffraction and ultrasonic velocity measurements of three silicate glasses (in jadeite, albite, and diopside compositions) show a sharp contrast in pressure-induced changes in structure and elasticity. With increasing pressure to around 6 GPa, polymerized glasses (jadeite and albite) display large shift in the first sharp diffraction peak (FSDP) in the structure factor, S(Q), to higher-Q values, indicating rapid shrinkage in the intermediate-range ordered (IRO) structure. Above 6 GPa, the shift of FSDP decelerates, suggesting that shrinkage in the IRO structure has been largely completed and the structure evolution is now dominated by the diminution of the interstitial volume in a more densely packed arrangement. Associated with this structural change, sound velocities increase with pressure above 6 GPa. In contrast, the depolymerized diopside glass exhibits smaller changes in the pressure dependence for both sound velocities and FSDP positions. Compared to the polymerized glasses, the velocities are faster and the positions of FSDP appear at higher-Q under the same experimental conditions. The results suggest that the depolymerized diopside glass has an initially denser IRO structure compared to that of the polymerized glasses, and there are no sufficient interstitial voids to shrink. The different behaviors between polymerized and depolymerized glasses are apparently related to the initial linkage of tetrahedra and the pressure-induced structural reactions. These results suggest that under compression up to 10 GPa, the degree of polymerization is a major factor affecting the IRO network structure and the sound velocity of silicate glasses.

Contrasting behavior of intermediate-range order structures in jadeite glass and melt

Structures of jadeite glasses and melt are studied by the multi-angle energy-dispersive X-ray diffraction technique under high pressures and temperatures. The temperature dependence of X-ray structure factors, S(Q), is obtained at experimental conditions from 4.5GPa and 300K to 6.3GPa and 2173K. When the glass sample is heated at high pressures, the first sharp diffraction peak (FSDP) in the structure factor becomes sharper and shifts to higher-Q with increasing temperature to 473K. At higher temperatures to 873K, both shape and position of the FSDP change only slightly. The structure factor of jadeite melt at 2173K and 6.3GPa clearly differs from that of the glass at 873K (just below melting). The FSDP of the melt is broader and located at lower-Q (corresponding to higher real-space atomic distance). In addition, a small peak (second sharp diffraction peak – SSDP) appears in the S(Q) of the melt between 3.0 and 3.2Å−1, which is known to be a sign for change of short-range ordering. Although the pressure drops to 3.7GPa upon quenching from the melt, the quenched glass exhibits densified features in the structure factor, with the FSDP located at a higher-Q than that of glass before melting at 873K and 5.3GPa. This implies that the intermediate-range order structure of the quenched glass (300K, 3.7GPa) is more densified by thermally-induced modification, although this quenched glass does not show clear SSDP in its S(Q). Similar to previous studies, the glass decompressed to ambient condition remains denser than the glass before compression and heating. The FSDP position changes from 2.02Å−1 in the starting material to 2.17Å−1 in the recovered glass, suggesting that the volume of recovered glass decreases about 20% in volume. The present result implies that glasses quenched under ambient pressure do not accurately represent structural behavior of melts under high pressure, while glasses quenched under high pressure can be treated as good analogs to melts at corresponding high pressure ranges, at least from the structural behavior point of view.

Correction: Corrigendum: Probing the different spatial scales of Kel F-800 polymeric glass under pressure

One of the fundamental open questions in condensed matter science is the origin of the unique universal characteristics of glasses. Among them, the Boson peak (BP) and the first sharp diffraction peak (FSDP) are directly related with the disordered nature of these solids. The lack of widely accepted understanding of the origin of these features makes the characterization of glass forming systems on the microscopic level challenging. Moreover a strong and open debate exists on the possible correlation between BP and FSDP and its origin. Here we present the first detailed concomitant Raman and x-ray diffraction study of these two features under hydrostatic pressure. Surprisingly, we find that the previously proposed correlations between the positions of BP and FSDP do not hold under pressure. Based on the anticorrelation of the characteristic dimensions, we conclude that, BP and FSDP probe different spatial scales corresponding to dynamical and structural dimensions, respectively.

Probing the different spatial scales of Kel F-800 polymeric glass under pressure

One of the fundamental open questions in condensed matter science is the origin of the unique universal characteristics of glasses. Among them, the Boson peak (BP) and the first sharp diffraction peak (FSDP) are directly related with the disordered nature of these solids. The lack of widely accepted understanding of the origin of these features makes the characterization of glass forming systems on the microscopic level challenging. Moreover a strong and open debate exists on the possible correlation between BP and FSDP and its origin. Here we present the first detailed concomitant Raman and x-ray diffraction study of these two features under hydrostatic pressure. Surprisingly, we find that the previously proposed correlations between the positions of BP and FSDP do not hold under pressure. Based on the anticorrelation of the characteristic dimensions, we conclude that, BP and FSDP probe different spatial scales corresponding to dynamical and structural dimensions, respectively.

Simultaneous structure and elastic wave velocity measurement of SiO2 glass at high pressures and high temperatures in a Paris-Edinburgh cell

An integration of multi-angle energy-dispersive x-ray diffraction and ultrasonic elastic wave velocity measurements in a Paris-Edinburgh cell enabled us to simultaneously investigate the structures and elastic wave velocities of amorphous materials at high pressure and high temperature conditions. We report the first simultaneous structure and elastic wave velocity measurement for SiO(2) glass at pressures up to 6.8 GPa at around 500°C. The first sharp diffraction peak (FSDP) in the structure factor S(Q) evidently shifted to higher Q with increasing pressure, reflecting the shrinking of intermediate-range order, while the Si-O bond distance was almost unchanged up to 6.8 GPa. In correlation with the shift of FSDP position, compressional wave velocity (Vp) and Poisson's ratio increased markedly with increasing pressure. In contrast, shear wave velocity (Vs) changed only at pressures below 4 GPa, and then remained unchanged at ~4.0-6.8 GPa. These observations indicate a strong correlation between the intermediate range order variations and Vp or Poisson's ratio, but a complicated behavior for Vs. The result demonstrates a new capability of simultaneous measurement of structures and elastic wave velocities at high pressure and high temperature conditions to provide direct link between microscopic structure and macroscopic elastic properties of amorphous materials.

Structural changes of SiO2 glass by mechanical milling

Structural changes of ground SiO2 glass were investigated using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. SiO2 glass samples were ground in a ball mill for up to 500 h. Reduction in the particle size of ground SiO2 glass samples was observed up to ∼ 80 h of milling. After 80 h of milling, the particle size of ground SiO2 glass remained almost constant at approximately 3 μm. The first sharp diffraction peak (FSDP) position (q1) of the XRD pattern for ground SiO2 glass shifted from 1.500 (original) to 1.544 (500 h of milling) A-1. The variation may be attributed to a change of the intermediate-range structure. The FSDP position of the 500 h ground SiO2 glass returned to the original value after annealing at 1000 °C. This annealing behavior includes two components. The variation in q1 for annealing up to ∼ 500 °C is small (0.0087 A-1) and may be attributed to an increase of the Si-O-Si angle. However, for annealing at 500-1000 °C, a large variation was observed (0.0350 A-1) and it may be attributed to a decrease of 3-membered rings. IR spectra of samples milled up to ∼ 80 h revealed sharpening of the ν = 1100 cm-1 band (Si-O stretching mode) and a decrease in the absorption of the ν = 800 cm-1 band (Si-O-Si bending mode). The IR analyses indicate the shrinkage of Si-O-Si linkages by milling. For over 80 h of milling, these variations are small. The particle size remains almost constant for over 80 h of milling, and therefore, only structural changes in a particle would be responsible for the changes in the IR spectra. The Raman spectra exhibited an increase in the luminescence intensity for milling up to ∼ 40 h. The luminescence may result from surface defect structures on SiO2 glass grains, and the increase in the luminescence intensity is consistent with particle size reduction by milling.

Radiation-modified structure of Ge25Sb15S60 and Ge35Sb5S60 glasses

Atomic structures of Ge(25)Sb(15)S(60) and Ge(35)Sb(5)S(60) glasses are investigated in the gamma-irradiated and annealed after gamma-irradiation states by means of high-energy synchrotron x-ray diffraction technique. The first sharp diffraction peak (FSDP) is detected at around 1.1 A(-1) in the structure factors of both alloys studied. The FSDP position is found to be stable for radiation/annealing treatment of the samples, while the FSDP intensity shows some changes between gamma-irradiated and annealed states. The peaks in the pair distribution functions observed between 2 and 4 A are related to the Ge-S, Ge-Sb, and Sb-Sb first neighbor correlations and Ge-Ge second neighbor correlations in the edge-shared GeS(42) tetrahedra, and S-S and/or Ge-Ge second neighbor correlations in the corner-shared GeS(42) tetrahedra. Three mechanisms of the radiation-/annealing-induced changes are discussed in the framework of coordination topological defect formation and bond-free solid angle concepts.

Transformation in intermediate-range structure of vitreous silica under high pressure andtemperature

The pressure dependence of the structure factor for vitreous silica was measured up to 8.3 GPa at500 °C by means of an in situ x-ray diffraction method. The position of the first sharp diffraction peak(FSDP) moved to a higher momentum transfer as the pressure increased. It moved rapidlybetween 3.3 and 5.8 GPa, and then the slope of the FSDP position as a function of pressuredecreased. The pressure dependence of the position is the same as that for a sample heated to500 °C after room-temperature compression. On decompression at500 °C, the position of the FSDP showed hysteresis. The pressure dependence of the FSDPposition suggests that the permanent densification of vitreous silica is realized due topreservation of the intermediate-range structure stabilized at high pressure andtemperature.

Compositional changes of the first sharp diffraction peak in binary selenide glasses

Compositional changes of the first sharp diffraction peak (FSDP) in the measured structure factor have been studied for several binary selenide glasses using pulsed-neutron and high-energy x-ray diffraction techniques. The observed variations in the FSDP (factor of 10 in the amplitude and $\ensuremath{\approx}0.5\phantom{\rule{0.3em}{0ex}}{\mathrm{\AA{}}}^{\ensuremath{-}1}$ in the peak position) reflect multiple aspects in the glass network on both the short- and intermediate-range scales and are also correlated with macroscopic properties. An empirical relation has been discovered relating the compositional dependence of the FSDP position to the local coordination number of the guest atom.

A structural comparison of supercooled water and intermediate density amorphous ices

New data are presented on neutron diffraction in ultrapure bulk supercooled heavy water measured down to 262 K. The data are analysed in terms of the trends observed in the first sharp diffraction peak (FSDP) parameters, the feature which dominates the measured neutron spectra. The neutron FSDP position, height and width are compared to literature data for supercooled water, water under pressure and to the same parameters obtained for recently discovered intermediate density amorphous ices. It is found that the FSDP parameters in supercooled water and the amorphous ices generally exhibit a similar behaviour, suggesting a new structural regime may occur in deeply supercooled water below Q 0 ∼ 1.83 Å−1 (T ∼ 251 K) associated with increased intermediate range ordering. It is argued that this structural regime may be linked to a similar trend in the density which appears when the density is plotted as a function of FSDP position. A detailed comparison of the neutron and X-ray structure factors for supercooled water and intermediate density amorphous ices with the same FSDP positions is also made. The diffraction data show that although the overall general structures are qualitatively very similar, the amorphous ice correlations are considerably sharper and extend to much higher radial distances.

Dynamical properties of vitreous silica around the first sharp diffraction peak

Inelastic neutron scattering measurements on vitreous silica have revealed that the contribution from the acoustic-like mode along the position of the first sharp diffraction peak (FSDP) is prominent below the boson peak energy and at low temperatures. Strong coupling between this acoustic-like mode at the FSDP position and the boson peak has also been confirmed, which implies the existence of Ioffe-Regel limits in glasses. We propose that the origin of the excitations along the FSDP position can be attributed to the harmonic vibrations at the surface of void spaces in glasses. We also consider that the FSDP in glasses arises from a quasi-periodicity, which is caused by the continuity of void spaces, corresponding to the lattice spacing of crystalline counterparts.

An X-ray diffraction study of shock-wave-densified SiO 2 glasses

The densification and structural changes in SiO2 glass compressed up to 43.4 GPa by shock experiments are investigated quantitatively by the X-ray diffraction technique. Direct structural data (average Si–O and Si–Si distances and Si–O–Si angles, coordination number of the Si atom) of these shock-densified SiO2 glasses have been obtained by analyzing the radial distribution function curves, RDF(r), calculated with X-ray diffraction data. The coordination number of all densified glasses is about 4 and shows almost no pressure variation. The SiO2 glass has shown density increase of 11% at a shock compression of 26.3 GPa. This density evolution could not be explained by the coordination change. The reduction of the average Si–O–Si angle (144° at 0 GPa to 136° at 26.3 GPa) obtained from RDF(r) data may account for this density increase. This Si–O–Si angle change may be caused by shrinkage of the network structure and the increase of small rings of SiO4 tetrahedra. For higher shock pressure, a decrease in the Si–O–Si angle to 140° was observed. This is consistent with the decrease in density at 32.0 and 43.2 GPa. This decrease in the Si–O–Si angle and density could be attributed to an annealing effect due to high after-shock residual temperature. This pressure dependence of average Si–O–Si angles in shock-densified SiO2 glass agrees with the results of our previous Raman spectroscopic study. On the other hand, the pressure variation for the first sharp diffraction peak (FSDP) was analyzed to estimate the evolution of intermediate range structures. It is suggested that the mean d value (d m ) obtained from the position of FSDP strongly depends on the shock and residual temperature, as well as shock pressure.

Real space manifestation of the first sharp diffraction peak in the structure factor of liquid and glassy materials

The problem of those discernible features of the intermediate range order (IRO) which can be attributed to the first sharp diffraction peak (FSDP) observed in the structure factor of many liquid and glassy materials is approached by treating this peak as a distinct feature. It is found, by considering the measured partial structure factors, S αβ ( k ), for molten ZnCl 2 , GeSe 2 , MgCl 2 , NiBr 2 and Nil 2 and the measured total structure factors, F ( k ), for glassy SiO 2 , PS 4 and liquid CCl 4 , that the propensity of the FSDP to have a prominent effect on the underlying features of the IRO depends noticeably on the system type. Specifically, the FSDP confers a marked oscillatory character of periodicity 2π/ k 1 (where k 1 is the FSDP position) on the IRO when the local structural units, which give rise to the density fluctuations on the IRO scale, exist as stable entities for a timescale τ ≫ 5 × 10 -12 s. The FSDP therefore accounts for the discernible features of the underlying IRO for the viscous glass forming liquids ZnCl 2 and GeSe 2 , for the glasses SiO 2 and PS 4 , and for the molecular liquid CCl 4 . The influence of the FSDP on the IRO is less pronounced for molten MgCl 2 and is negligible for molten NiBr 2 and Nil 2 , both of which have a high cation mobility which leads to a relative instability of the Ni 2+ centred structural units. The effect on the FSDP of temperature and pressure are briefly considered as are the development of the FSDP in molten ZnX 2 (when X is changed from Cl to I to Br) and the minimum size of r -space model which is required if the FSDP is to be accurately predicted.

A correlation between low-energy vibrational spectra and first sharp diffraction peak in chalcogenide glasses

For the first time comparison of some properties of the low-energy vibrational excitations and the first sharp diffraction peak (FSDP) in glasses is carried out. It is found out that the position of low-frequency (boson) peak in Raman spectra correlates with the position of FSDP and changes of the boson peak intensity correlate with that of FSDP. These correlations confirm a connection of low-energy (2–10 meV) anomalies of vibrational spectra of glasses with characteristic length in their structure.