Anharmonicity and local lattice distortion in strained Ge-dilute Si1−Ge  alloy

Dong, Juncai; Guo, Zhiying; Zhang, Xiaoli; An, Pengfei; Gong, Yu; Zhu, Hai‐Liang; Li, Pengshan; Chen, Dongliang

doi:10.1016/j.jallcom.2015.08.253

Cited by 2 publications

(2 citation statements)

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“…With an elongation of 0.167 Å for the average Ti–Si1 bond distance and an angle bending of 3° for average Ti–O1–Si1 angles, this tendency is also observed in the local structural relaxation for site T11. It indicates the atomic-size-mismatch strain between Ti and Si is relaxed dominantly by radical bond distance variation rather than by bond-angle bending as occurred in many covalent systems …”

Section: Results and Discussionmentioning

confidence: 99%

“…It indicates the atomic-size-mismatch strain between Ti and Si is relaxed dominantly by radical bond distance variation rather than by bond-angle bending as occurred in many covalent systems. 71 Because the DFT studies are thermodynamic studies in nature, the excellent agreement between EXAFS and DFT suggest that the distribution of Ti in MFI is governed dominantly by thermodynamic stability. However, there exist some discrepancies between EXAFS and DFT about the preference order for the remaining sites, implying that other factors, such as interdefects, the nature of the structuredirecting agent used in the synthesis, the kinetics of formation of structural precursors, and sorbed species inside the zeolite cavities close to Ti centers, can also affect the Ti distribution.…”

Section: Resultsmentioning

confidence: 99%

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Toward a Unified Identification of Ti Location in the MFI Framework of High-Ti-Loaded TS-1: Combined EXAFS, XANES, and DFT Study

et al. 2016

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Titanium silicalite-1 (TS-1) has been shown to be a heterogeneous catalyst with remarkable efficiency and selectivity; however, the nature of the active Ti site in the MFI framework remains elusive. Here we report combined experimental and theoretical research on Ti distribution in the 12 crystallographically distinct T sites of the MFI framework in high-Ti-loaded TS-1 (2.7 wt % in TiO2). Using a multishell fit to extended X-ray absorption fine structure, we show that T4 is the most populated site, in marked contrast to the preferential substitution sites and the definitely excluded sites assumed hitherto by diffraction studies. The identification is supported by a good agreement between calculated and experimental X-ray absorption near-edge structure studies and by full periodic density functional theory (DFT) computation. In spite of having the identical most favored site, the preference order for the remaining sites predicted by DFT does not fully match the experimental results. This suggests that Ti distribution in the resulting TS-1 framework is positively correlated with the thermodynamic stability of pure material but can be affected by other factors such as interdefects. These new insights may facilitate the bottom-up design of new zeolites with tailored catalytic performance and studies on mechanisms of various oxidation reactions.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%