Probing of Triply Coordinated Oxygen in Amorphous Al<sub>2</sub>O<sub>3</sub>

Lee, Sung Keun; Ryu, Saebom

doi:10.1021/acs.jpclett.7b03027

Cited by 44 publications

(42 citation statements)

References 56 publications

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“…Nonetheless, pure Al 2 O 3 cannot be obtained as a bulk glass, even under very fast cooling conditions (Sun, 1949;Rosenflanz et al, 2004), despite the fact that the liquid can be supercooled several hundred degrees below its melting point (Krishnan et al, 2005). Alumina can, however, be produced in amorphous forms by anodic oxidation (Lamparter and Kniep, 1997), magnetron sputtering (Lee et al, 2009(Lee et al, , 2010Lee and Ryu, 2017) and sequential infiltration synthesis (Berman et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The Structure of Amorphous and Deeply Supercooled Liquid Alumina

et al. 2019

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Liquid Al 2 O 3 has been supercooled more than 500 K below its melting point (T m = 2,327 K) using aerodynamic levitation and laser heating techniques. High energy synchrotron x-ray measurements were performed over a temperature range of 1,817 ≤ T (K) ≤ 2,700 and stroboscopic neutron diffraction at 1,984 and 2,587 K. The diffraction patterns have been fitted with Empirical Potential Structure Refinement (EPSR) models and compared to classical Molecular Dynamics (MD) simulation results. Both sets of models show similar trends, indicating the presence of high populations of AlO 4 and AlO 5 polyhedral units predominantly linked by triply shared oxygen atoms. EPSR reveals that the mean Al-O coordination number changes linearly with temperature with n AlO = 4.41-[1.25 × 10 −4 ] (T-T m), with a 2.5 Å cutoff. Both EPSR and MD simulations reveal a direction of the temperature dependence of the aluminate network structure which moves further away from the glass forming ideal (n AlO = 3) during supercooling. Furthermore, we provide new experimental data and models for amorphous alumina grown by sequential infiltration synthesis of a polymer template. The amorphous solid form likely has a larger Al-O coordination number than the liquid, consistent with expectations for the hypothetical glass.

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Section: Introductionmentioning

confidence: 99%

The Structure of Amorphous and Deeply Supercooled Liquid Alumina

et al. 2019

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“…In Paper I, we introduced a modification to the Jacobi step (5) where certain terms are shifted from one iteration to another such that the converged amplitudes are equal to…”

Section: Sub-iteration In the Amplitude Equationsmentioning

confidence: 99%

“…Higher-order coupled cluster methods, [1,2,3] that is, methods beyond the coupled cluster singles and doubles level (CCSD), [4,5] are important tools for obtaining extremely accurate theoretical predictions of thermochemical and kinetic parameters. [6,7,8,9,10,11,12] Additionally, such methods provide reliable benchmark values for the development of lower-cost approximations.…”

Section: Introductionmentioning

confidence: 99%

Accelerating the convergence of higher-order coupled cluster methods

Matthews

Stanton

2015

The Journal of Chemical Physics

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The problem of the generally inferior convergence behavior of higher-order coupled cluster methods, such as CCSDT and CCSDTQ, compared to CCSD is analyzed in terms of Møller-Plesset perturbation theory. A new structure for the CCSDT and CCSDTQ equations (and various approximations of these) is proposed which reorders contributions between the various cluster amplitudes and emphasizes lower-order corrections to the energy at each iteration. Numerical testing of the proposed method compared to the widely used direct inversion in the iterative subspace convergence acceleration technique shows significant improvement in the rate of convergence and total time-to-solution, especially for methods including quadruple excitations.

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“…(Right-bottom) 17 O 3QMAS NMR spectra for crystalline -Al2O3 and amorphous Al2O3. Various symbols refer to oxygen sites for crystalline aluminosilicates and aluminates (modified from [9]). 수행되었다.…”

mentioning

confidence: 99%

“…Al, [5] Al, [6] Al)이 관찰된다. [9] 상대적으로 많은 [5] Al 존재는 유리질 Al2O3에서 산소환경이 배위수가 2인 [2] O뿐 아니라 주로 고압 환경에서 생성되는 것으로 유추되는 [3] O로 존재하는 것을 지 시한다. 그림 4의 O-17 NMR 연구로부터 비정질 Al2O3에 …”

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