Multinuclear Magnetic Resonance Crystallographic Structure Refinement and Cross-Validation Using Experimental and Computed Electric Field Gradients: Application to Na2Al2B2O7

摘要: An NMR crystallographic method is presented for the refinement of structures using electric field gradient (EFG) tensors measured solid-state spectroscopy and those calculated projector-augmented wave DFT method. As EFG data often overestimate experimental data, former are scaled to yield optimal agreement a test set compounds having highly accurate data. A least-squares optimization procedure then performed minimize difference between tensors. This yields high- quality crystal comparable obtained from pure energy minimizations, as judged by their rmsd single-crystal X-ray structures, based on observables. Further improvement simultaneously refining against tensor parameters optimizing lattice with DFT. We use this hybrid experimental−theoretical approach refine structure Na2Al2B2O7, member an important family nonlinear optical materials, which has been focus study due its tendency form stacking faults. The resulting subjected systematic cross-validation process 23 Na, 11 B, 17 O, 27 Al chemical shift thereby demonstrating validity our strategy. may be useful intrinsically polycrystalline materials typically only low obtainable through traditional diffraction- methods.