Extended x-ray absorption fine structure, x-ray diffraction and reverse Monte Carlo studies of an amorphous Ga<sub>50</sub>Se<sub>50</sub>alloy produced by mechanical alloying

Machado, K.D.; Jóvári, P.; Lima, J.C. de; Campos, Carlos Eduardo Maduro de; Grandi, T.A.

doi:10.1088/0953-8984/16/4/007

Cited by 18 publications

(16 citation statements)

References 50 publications

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“…If we compare our results with those found by MD simulations of l-GeSe 4 21 , in which it is found N Ge-Ge = 0.06, N Ge-Se = 3.87 and N Se-Se = 1.04, a large increase in the homopolar coordination numbers is seen, suggesting that the liquid and the amorphous alloy produced by MA have important differences from the structural point of view. This was also verified in an amorphous Ga 50 Se 50 alloy produced by MA studied recently by us 50 .…”

Section: Pair Distribution Functionssupporting

confidence: 72%

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Machado

Lima

Campos

et al. 2005

Solid State Communications

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The short and intermediate range order of an amorphous GeSe4 alloy produced by Mechanical Alloying were studied by Reverse Monte Carlo simulations of its x-ray total structure factor and Raman scattering. The simulations were used to compute the G RMC Ge-Ge (r), G RMC Ge-Se (r) and G RMC Se-Se (r) partial distribution functions and the S RMC Ge-Ge (K), S RMC Ge-Se (K) and S RMC Se-Se (K) partial structure factors. We calculated the coordination numbers and interatomic distances for the first and second neighbors and the bond-angle distribution functions Θ ijl (cos θ). The data obtained indicate that the structure of the alloy has important differences when compared to alloys prepared by other techniques. There are a high number of Se-Se pairs in the first shell, and some of the tetrahedral units formed seemed to be connected by Se-Se bridges.

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Section: Pair Distribution Functionssupporting

confidence: 72%

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Machado

Lima

Campos

et al. 2005

Solid State Communications

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“…Such agreement reinforces the structural data obtained from the EXAFS analysis using the cumulant expansion method and from the RMC simulations. Let us compare the present data with those obtained for a-Ga 50 Se 50 by Machado et al 36 By using an EXAFS analysis without cumulant expansion, they found ⟨N Se-Se ⟩ = 1.5, ⟨N Se-Ga ⟩ = 2.4, and ⟨N Ga-Ga ⟩ = 1.6, for coordination numbers, and ⟨r Se-Se ⟩ = 2.40 Å, ⟨r Se-Ga ⟩ = 2.46 Å, and ⟨r Ga-Ga ⟩ = 2.39 Å, for interatomic distances. From RMC simulations, they found ⟨N Se-Se ⟩ = 1.3, ⟨N Se-Ga ⟩ = 2.5, and ⟨N Ga-Ga ⟩ = 1.2, for coordination numbers, and ⟨r Se-Se ⟩ = ⟨r Se-Ga ⟩ = ⟨r Ga-Ga ⟩ = 2.42 Å, for interatomic distances.…”

Section: B Rmc Simulationssupporting

confidence: 64%

“…Some Ga-Se allows were studied in this way. 15,16,[35][36][37] Due to its selectivity, EXAFS is a powerful tool for obtaining the local atomic order around a specific atomic species. 33,34 EXAFS oscillations χ(k) obtained on an edge of an element A furnish information about interactions involving only the element A, and the procedure used to extract such information is almost the same for crystalline or amorphous samples.…”

Section: Introductionmentioning

confidence: 99%

“…These functions indicated that the structural units found in a-GaSe 9 are similar to those found in trigonal Se and/or Se chains or rings, and essentially discard the presence of tetrahedral units, which appear in the amorphous Ga 50 Se 50 alloy (a-Ga 50 Se 50 ). 36 This paper is organized as follows. Section II describes the theoretical fundamentals related to the EXAFS analysis and cumulant expansion (Sec.…”

Section: Introductionmentioning

confidence: 99%

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Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations

Siqueira

Maia

Araújo

et al. 2015

The Journal of Chemical Physics

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In this article, we investigated structural and thermal properties of an amorphous alloy of the Ga-Se system. The amorphous GaSe9 alloy was produced by mechanical alloying and it was studied using EXAFS spectroscopy and cumulant expansion method. We also made reverse Monte Carlo simulations using the total structure factor S(K) obtained from x-ray diffraction and the EXAFS χ(k) oscillations on Se and Ga K edges as input data. Several parameters, such as average coordination numbers and interatomic distances, structural and thermal disorders, asymmetry of the partial distribution functions gij(r), and Einstein and Debye temperatures, were determined. The gij (E)(r) functions were reconstructed from the cumulants C1, C2, and C3 obtained from the Einstein model, and they were compared to the gij (RMC)(r) functions obtained from the simulations. The simulations also furnished the partial bond angle distribution functions Θijℓ(cosθ), which describe the angular distribution of bonds between first neighbors, and give information about the kind of structural units present in the alloy.

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“…Before the simulation, a box, containing 5000 atoms following its composition and hard sphere dense-packed ͑HSDP͒ model, was built. Least-square fitting for S͑Q͒ and ͑k͒ data as carried out under the constraint of atomic density calculated from experimental G͑r͒, 31 which is about 0.0518 Å −3 for Zr 70 Ni 30 . The minimum atomic distances were set to be 2.8, 2.5, and 2.2 Å for Zr-Zr, Zr-Ni, and Ni-Ni pairs, respectively.…”

Section: Methodsmentioning

confidence: 99%

Atomic structure in Zr70Ni30 metallic glass

Yang

Yin

Wang

et al. 2007

Journal of Applied Physics

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Atomic structure of Zr 70 Ni 30 metallic glass ͑MG͒ was investigated by reverse Monte Carlo simulation combining with x-ray diffraction and Ni and Zr K-edge extended x-ray absorption of fine structure measurements. Distributions of coordination number ͑CN͒ and Voronoi clusters were analyzed by Voronoi tessellation method. The average CN of atoms was obtained to be 11.4 together with the average CN of Zr and Ni atoms of about 11.8 and 10.6, respectively. It is found that Z11 Kasper polyhedron and distorted icosahedra are mainly favored structural units in INTRODUCTIONAtomic structure of metallic glasses ͑MGs͒ has been studied experimentally and theoretically 1-4 because their extraordinary mechanical and magnetic properties strongly depend on their atomic structures. Gaskell proposed that atomic structure of MG is similar with that of corresponding crystalline phases. 5 Stability of MG is linked with its atomic structure, 6,7 which correlates with atomic structure of the corresponding crystalline phase by annealing. 8,9 For example, icosahedral clusters are found to be dominant atomic structure in Zr 70 Cu 29 Pd 1 MG, 10,11 which leads to primary phase transition by forming icosahedral quasicrystal 12,13 after annealing, while Zr 70 Ni 30−x Pd x ͑x Ͻ 10 at. % ͒ MGs do not exhibit such primary precipitation. 8 Furthermore, Zr-Cu binary MGs exhibit a glass transition event, whereas Zr-Ni binary MGs do not, 14 which might be due to their different atomic structures. 8 Thus, studies of atomic structure in such simple MGs are strongly demanded, which will promote our understanding to multicomponent bulk metallic glasses. However, structure of Zr-Ni MGs is still not completely understood [15][16][17][18] in spite of its wide amorphous-forming compositional range. 19 In the present work, we report the atomic structure of a Zr 70 Ni 30 MG by reverse Monte Carlo ͑RMC͒ simulation combining with x-ray diffraction ͑XRD͒ and extended x-ray absorption of fine structure ͑EXAFS͒ as well as Voronoi tessellation method. EXPERIMENTZr 70 Ni 30 ingot was prepared by arc melting high-purity metals ͑99.8% Zr and 99.9% Ni͒. Amorphous ribbons with a cross section of 0.03ϫ 2 mm 2 were obtained from these alloys by single-roller melt spinning at a wheel surface velocity of 30 m / s in purified Ar atmosphere. The oxygen content of the as-prepared ribbon samples was analyzed to be less than 800 mass ppm by inductively coupled plasma spectroscopy. The influence of oxygen on the transformation behavior can thus be disregarded. 20,21 Room-temperature high resolution XRD measurements were carried out for as-prepared Zr 70 Ni 30 sample with high energy x-ray ͑100 keV͒ at beamline BW5, Hasylab in Germany. Diffraction patterns were recorded by a Mar2300 image plate. Beamstop was located away from the center to record data with larger Q ͑wave vector transfer͒ range, resulting in high resolution in real-space reduced pair distribution function G͑r͒. XRD patterns were integrated to Q-space data file after subtracting its background by the program FIT...

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Extended x-ray absorption fine structure, x-ray diffraction and reverse Monte Carlo studies of an amorphous Ga₅₀Se₅₀alloy produced by mechanical alloying

Cited by 18 publications

References 50 publications

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations

Atomic structure in Zr70Ni30 metallic glass

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Extended x-ray absorption fine structure, x-ray diffraction and reverse Monte Carlo studies of an amorphous Ga50Se50alloy produced by mechanical alloying

Cited by 18 publications

References 50 publications

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations

Atomic structure in Zr70Ni30 metallic glass

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Product

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Extended x-ray absorption fine structure, x-ray diffraction and reverse Monte Carlo studies of an amorphous Ga₅₀Se₅₀alloy produced by mechanical alloying