Structure of amorphous oxide Al2O3: Results of a molecular-dynamics experiment

Prokhorskii, M. E.; Fofanov, A. D.; Алешина, Л. А.; Nikitina, E. A.

doi:10.1134/1.1780628

Cited by 6 publications

(2 citation statements)

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“…The bulk and surface thermodynamics of a-Al 2 O 3 have not yet been experimentally investigated to the best of our knowledge. However, the structure of a-Al 2 O 3 has been studied extensively, with major focus on probing the chemical environments of the Al and O ions using a variety of spectroscopic and computational techniques including solid-state nuclear magnetic resonance (NMR), − X-ray photoelectron spectroscopy (XPS), X-ray and neutron diffraction, , extended X-ray absorption fine structure (EXAFS), molecular dynamic simulations, − first-principles calculations of XPS and NMR spectra, and ab initio calculations . These investigations are overall in good agreement, indicating that the amorphous structure is composed of AlO 4 tetrahedra, AlO 5 polyhedra, and AlO 6 octahedra with predominant fractions of AlO 4 and AlO 5 units.…”

Section: Introductionmentioning

confidence: 96%

Amorphous Alumina Nanoparticles: Structure, Surface Energy, and Thermodynamic Phase Stability

et al. 2013

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To provide a complete picture of the energy landscape of Al 2 O 3 at the nanoscale, we directed this study toward understanding the energetics of amorphous alumina (a-Al 2 O 3 ). a-Al 2 O 3 nanoparticles were obtained by condensation from gas phase generated through laser evaporation of α-Al 2 O 3 targets in pure oxygen at25 Pa. As-deposited nanopowders were heat-treated at different temperatures up to 600 °C to provide powders with surface areas of 670−340 m 2 /g. The structure of the samples was characterized by powder X-ray diffraction, transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. The results indicate that the microstructure consists of aggregated 3−5 nm nanoparticles that remain amorphous to temperatures as high as 600 °C. The structure consists of a network of AlO 4 , AlO 5 , and AlO 6 polyhedra, with AlO 5 being the most abundant species. The presence of water molecules on the surfaces was confirmed by mass spectrometry of the gases evolved on heating the samples under vacuum. A combination of BET surface-area measurements, water adsorption calorimetry, and high-temperature oxide melt solution calorimetry was employed for thermodynamic analysis. By linear fit of the measured excess enthalpy of the nanoparticles as a function of surface area, the surface energy of a-Al 2 O 3 was determined to be 0.97 ± 0.04 J/m 2 . We conclude that the lower surface energy of a-Al 2 O 3 compared with crystalline polymorphs γand α-Al 2 O 3 makes this phase the most energetically stable phase at surface areas greater than 370 m 2 /g.

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Section: Introductionmentioning

confidence: 96%

Amorphous Alumina Nanoparticles: Structure, Surface Energy, and Thermodynamic Phase Stability

et al. 2013

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“…MD experiments were conducted using the program designed at Department of Solid State Physics of Petrozavodsk State University (A.D. Fofanov, M.E. Prokhorskiy [32]). MD simulation of mechanically activated titanite was carried out in the canonical ensemble NV T (N is the number of particles, V is the volume, and T is absolute temperature).…”

Section: Methods Of a Structural Model Construction And Theoretical X-ray Patterns Calculationmentioning

confidence: 99%

Х-ray Study and Computer Simulation of the Structure of Amorphous-Crystalline Titanite

Сидорова

Алешина

Fofanov

2022

Физика Твердого Тела

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The structure of amorphous-crystalline titanite obtained by mechanical activation was studied by X-ray diffraction and simulation methods. The short-range order characteristics were calculated using Finbak-Warren's method. It was found that the coordination numbers of metal atoms decreased as the result of titanite grinding. The atomic configurations of short-range order of ground titanite were constructed by translation of titanite unit cell. The theoretical X-ray patterns were calculated using Debye's method and were compared with the experimental curves. The structure of ground titanite in the mill with centrifugal factor 40 g was described satisfactorily by the model of mechanical mixture of clusters containing 2016 atoms, disordered during the molecular dynamics with clusters containing 12096 atoms. The increase of grinding intensity led to the sharp decrease of sizes of small cluster.

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Relationship Between Al $$_{2}$$ O $$_{3}$$ Bulk and Interface Properties

Black

2016

Springer Theses

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Structure of amorphous oxide Al2O3: Results of a molecular-dynamics experiment

Cited by 6 publications

References 3 publications

Amorphous Alumina Nanoparticles: Structure, Surface Energy, and Thermodynamic Phase Stability

Amorphous Alumina Nanoparticles: Structure, Surface Energy, and Thermodynamic Phase Stability

Х-ray Study and Computer Simulation of the Structure of Amorphous-Crystalline Titanite

Relationship Between Al $$_{2}$$ O $$_{3}$$ Bulk and Interface Properties

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