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Title: Monitoring the refinement of crystal structures with {sup 15}N solid-state NMR shift tensor data

The {sup 15}N chemical shift tensor is shown to be extremely sensitive to lattice structure and a powerful metric for monitoring density functional theory refinements of crystal structures. These refinements include lattice effects and are applied here to five crystal structures. All structures improve based on a better agreement between experimental and calculated {sup 15}N tensors, with an average improvement of 47.0 ppm. Structural improvement is further indicated by a decrease in forces on the atoms by 2–3 orders of magnitude and a greater similarity in atom positions to neutron diffraction structures. These refinements change bond lengths by more than the diffraction errors including adjustments to X–Y and X–H bonds (X, Y = C, N, and O) of 0.028 ± 0.002 Å and 0.144 ± 0.036 Å, respectively. The acquisition of {sup 15}N tensors at natural abundance is challenging and this limitation is overcome by improved {sup 1}H decoupling in the FIREMAT method. This decoupling dramatically narrows linewidths, improves signal-to-noise by up to 317%, and significantly improves the accuracy of measured tensors. A total of 39 tensors are measured with shifts distributed over a range of more than 400 ppm. Overall, experimental {sup 15}N tensors are at least 5 timesmore » more sensitive to crystal structure than {sup 13}C tensors due to nitrogen’s greater polarizability and larger range of chemical shifts.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Chemistry, University of Central Florida, 4104 Libra Drive, Orlando, Florida 32816 (United States)
  2. Department of Chemistry, Washington and Jefferson College, 60 Lincoln Street, Washington, Pennsylvania 15301 (United States)
  3. Department of Chemistry, Penn State University, University Park, Pennsylvania 16802 (United States)
  4. (United States)
Publication Date:
OSTI Identifier:
22493258
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 19; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMS; BOND LENGTHS; CARBON 13; CHEMICAL SHIFT; CRYSTAL STRUCTURE; DECOUPLING; DENSITY FUNCTIONAL METHOD; HYDROGEN 1; LINE WIDTHS; MONITORING; NEUTRON DIFFRACTION; NITROGEN; NITROGEN 15; NUCLEAR MAGNETIC RESONANCE; POLARIZABILITY; SOLIDS; TENSORS