Darstellung und Kopplung von Cyclosilazanen und Borazinen - Precursoren für Si-B-N- und Si-B-C-N-Keramiken

Jaschke, Bettina

doi:10.53846/goediss-2131

Cited by 1 publication

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“…The average density of our models is 2.5 g cm −3 , which is much larger than the surprisingly low experimental density of 1.9 g cm −3 of a-Si 3 B 3 N 7 powder [38]. At the beginning of our investigations we performed some shorter optimizations with scaled models that had the correct density of 1.9 g cm −3 , but with these models it was very difficult to achieve reasonable agreement with experimental data, so we decided to use the model with the larger density.…”

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confidence: 65%

Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data

Doerr¹,

Marian²

2007

J. Phys.: Condens. Matter

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We present an enhanced reverse Monte Carlo approach that includes fitting to NMR data in the form of chemical shifts in addition to the usually used scattering data. Furthermore, the internal energy is accounted for in the cost function to prevent unphysical structures. This approach was applied to generate structural models of amorphous Si 3 B 3 N 7 , which is a prototype of a new class of high performance ceramics exhibiting interesting features like high thermal and mechanical stability.We fitted our structural models in direct space to radial distribution functions from x-ray, neutron and electron scattering experiments, and to the 15 N NMR spectrum of the ceramic. This spectrum could not be interpreted before since it exhibits a broad structureless signal which is a superposition of peaks related to different chemical environments NB x Si 3−x (x = 0-3) whose chemical shifts were only partly known experimentally. Therefore we based the calculation of NMR data in the reverse Monte Carlo optimizations on previous theoretical work that was done in our group. All generated models reproduce the experimental radial distribution functions very well. This good agreement does not deteriorate when the NMR data are taken into account. Fitting the models to 15 N NMR chemical shifts in addition to scattering data results in structural changes that not only improve the agreement with the experimental magic-angle spinning (MAS) NMR spectrum but yield also significantly better second-nearest neighbour coordination statistics. M Supplementary data are available from stacks.

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Section: Free Volumecontrasting

confidence: 65%

Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data

Doerr¹,

Marian²

2007

J. Phys.: Condens. Matter

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Darstellung und Kopplung von Cyclosilazanen und Borazinen - Precursoren für Si-B-N- und Si-B-C-N-Keramiken

Cited by 1 publication

References 23 publications

Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data

Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data

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Darstellung und Kopplung von Cyclosilazanen und Borazinen - Precursoren für Si-B-N- und Si-B-C-N-Keramiken

Cited by 1 publication

References 23 publications

Reverse Monte Carlo modelling of amorphous Si3B3N7using scattering and15N NMR data

Reverse Monte Carlo modelling of amorphous Si3B3N7using scattering and15N NMR data

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Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data

Reverse Monte Carlo modelling of amorphous Si₃B₃N₇using scattering and¹⁵N NMR data