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Improved Electrostatic Embedding for Fragment-Based Chemical Shift Calculations in Molecular Crystals
journal contribution
posted on 2017-11-14, 21:43 authored by Joshua
D. Hartman, Ashwin Balaji, Gregory J. O. BeranFragment-based
methods predict nuclear magnetic resonance (NMR)
chemical shielding tensors in molecular crystals with high accuracy
and computational efficiency. Such methods typically employ electrostatic
embedding to mimic the crystalline environment, and the quality of
the results can be sensitive to the embedding treatment. To improve
the quality of this embedding environment for fragment-based molecular
crystal property calculations, we borrow ideas from the embedded ion
method to incorporate self-consistently polarized Madelung field effects.
The self-consistent reproduction of the Madelung potential (SCRMP)
model developed here constructs an array of point charges that incorporates
self-consistent lattice polarization and which reproduces the Madelung
potential at all atomic sites involved in the quantum mechanical region
of the system. The performance of fragment- and cluster-based 1H, 13C, 14N, and 17O chemical
shift predictions using SCRMP and density functionals like PBE and
PBE0 are assessed. The improved embedding model results in substantial
improvements in the predicted 17O chemical shifts and modest
improvements in the 15N ones. Finally, the performance
of the model is demonstrated by examining the assignment of the two
oxygen chemical shifts in the challenging γ-polymorph of glycine.
Overall, the SCRMP-embedded NMR chemical shift predictions are on
par with or more accurate than those obtained with the widely used
gauge-including projector augmented wave (GIPAW) model.
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Keywords
point chargesembedding treatment13 CElectrostatic Embedding15 N onescluster-based 1 H17 O chemical shiftsγ- polymorphembedding environment14 Nembedding model resultsFragment-Based Chemical Shift Calculations17 O chemical shift predictionsSCRMP-embedded NMR chemical shift predictionscrystal property calculationsion methodlattice polarizationchemical shielding tensorsgauge-including projectorGIPAWperformancePBE 0Molecular Crystals Fragment-based methodsSuch methodsoxygen chemical shiftsdensity functionalsMadelung field effects
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