Ab initio prediction of15N-NMR chemical shift in ?-boron nitride based on an analysis of connectivities

The 15N chemical shifts in mixed NB2Si and NBSi2 environments of Si3B3N7—A theoretical investigation

“…But it is also well known that there are cases where electron correlation plays a decisive role and the Hartree-Fock method badly fails. 3 To get an impression of the performance and the limitations of the applied quantum chemical method, we did some benchmarking on small molecules. These molecules were selected to resemble the crystal structures under consideration, i.e., we scanned the literature for molecules containing NB 2 Si and NBSi 2 building units.…”

“…Because the crystalline materials treated in this paper are purely hypothetical, a test of the method by comparing to experimental data was not possible. However, previous work in this group on similar systems [3,4] had shown that the approach gives reliable results. Furthermore, we employ internal criteria, such as the convergence of the calculated chemical shifts with the cluster size, to check the consistency of our calculations.…”

“…Dangling bonds at the cluster surface were saturated with hydrogen atoms. Previous calculations of NMR shifts done in our group [3,4] had shown that at least the second coordination sphere around the central atom should only consist of nonhydrogen atoms, so this determined the lower size limit for the clusters. This systematic approach was only applied to clusters centered around the two crystallographically inequivalent nitrogen atoms in b-2-Si 3 B 3 N 7 .…”

“…In our group, cluster models were used successfully for predicting NMR chemical shifts of crystalline boron nitride [3,4]. Encouraged by these experiences we set about calculating the 15 environments in the solid state.…”

A Solid-State Multinuclear Magnetic Resonance Investigation of Hexamethylborazine

“…23,24 Recently, borazine has been successfully used as a precursor for the synthesis of boron nitride, 25 a widely studied ceramic with valuable properties. [26][27][28][29] The quality of ceramics has been demonstrated to depend considerably on the architecture of the polymer; 30 hence, the choice of characterization tools is critical for monitoring and controlling polymerization and polymer-toceramic conversion. Fazen et al proposed a route to hexagonal boron nitride (h-BN) by thermal polymerization of borazine to form polyborazylene, 25 a polymer composed of linked borazine rings, followed by pyrolysis under an inert atmosphere, to yield the desired product.…”