The structure of Ge20SexTe80−x (x = 5, 10, 15, 20) glasses has been investigated by X-ray and neutron diffraction as well as Ge and Se K-edge extended X-ray absorption fine structure (EXAFS) ...measurements. Experimental datasets have been fitted simultaneously by the reverse Monte Carlo simulation technique. It has been found that all components obey the 8-N rule. Se binds preferentially to Ge. At x = 20, experimental data can be fitted without Se-Te bonding, but Se-Se bonds appear, and the Te-Te coordination number starts to increase. These observations show that though Se and Te are completely miscible in the liquid and in the solid phases the presence of Ge induces nanoscale phase separation.
•The Raman, XRD and EXAFS data Ge-As-S glasses were obtained and were analyzed.•As-rich and Ge-rich glasses based on AsS3 and GeS4 units, respectively.•Compositional changes result in the evolution ...of the observed Raman bands.
Structural order in the chalcogenide glasses of (As2S3)x(GeS2)1−x (x = 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) system is examined in terms of the parameters of local atomic structure as a function of composition x, obtained using high-resolution Raman spectroscopy, high-energy synchrotron X-ray diffraction, extended X-ray absorption fine structure spectroscopy and reverse Monte-Carlo modeling of diffraction data. As a result of the research carried out it is revealed that the structural order of As-rich (x > 0.4) and Ge-rich (x < 0.4) glasses is organized by the main As−S and Ge−S structural motifs based on pyramidal AsS3 and tetrahedral GeS4 units linked by =As−S−As= and Ge−S−Ge structural configurations, respectively; while for the intermediate compound with x = 0.4 the structural network seems to be better homogeneous on the nanoscale due to appearance of Ge−S−As= mixed structural configurations resulting in misbalance between corner-shared and edge-shared tetrahedral units in comparison with their predicted ratio for binary GeS2 glass and the structure of this alloy is similar to the structure of the stoichiometric glass Ge18.2As18.2S63.6 (i.e., x = 0.455) consisting of a coner-shared network of homogeneously mixed GeS4 tetrahedra and AsS3 pyramids. Based on the structural studies, it is also established that the balance between corner-shared and edge-shared GeS4 tetrahedra in the glass backbone of the investigated GeS2-based glasses seems to be responsible for the interconnectivity between two speculative Raman modes at 370 and 430 cm−1. Compositional changes in studied glasses result in the evolution of the observed Raman bands. Such dependences of characteristic constituent Raman bands’ intensities showed that (As2S3)x(GeS2)1−x samples contain different nanophases whose concentration is changing along chosen compositional cross-section.
We report an investigation of the short-range order of liquid Cu–Sn alloys carried out by means of X-ray and neutron diffraction. The diffracted X-ray intensity was evaluated with a model assuming ...micro-inhomogeneities in the material. Furthermore, the reverse Monte Carlo modelling technique was applied to derive partial correlation functions. The alloys under investigation are found to be micro-heterogeneous with clusters of Cu3Sn stoichiometry distributed among the remaining Sn atoms.
Chemical short range order and topology of GexGaxTe100-2x glasses was investigated by neutron- and x-ray diffraction as well as Ge and Ga K-edge extended x-ray absorption fine structure (EXAFS) ...measurements. Large scale structural models were obtained by fitting experimental datasets simultaneously with the reverse Monte Carlo simulation technique. Models, relying only on experimental data and basic physical information without constraining the average coordination numbers, give 3.9–4.1 for the number of the atoms in the first coordination sphere of Ge atoms, while the average number of first neighbors of Ga atoms scatters around 3.8. The average coordination number of Te atoms is significantly higher than 2 for x = 12.5 and 14.3. It is found that the vast majority of MTe4 (M = Ge or Ga) tetrahedra have at least one corner sharing MTe4 neighbor.
Neutron scattering measurements were performed for a number of water–pyridine mixtures using hydrogen/deuterium substitution for water. Composite partial pair correlation functions were extracted ...using the MCGR procedure. The results show changes in the water structure compared to the pure liquid and specific water–pyridine and pyridine–pyridine interactions. There is a strong scattering at low
Q-values (<0.4 Å
−1) which varies with pyridine concentration. These results are interpreted in terms of spherical clusters within the water matrix.
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