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On the accuracy factors and computational cost of the GIAO–DFT calculation of 15 N NMR chemical shifts of amides
Author(s) -
Samultsev Dmitry O.,
Semenov Valentin A.,
Krivdin Leonid B.
Publication year - 2017
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4625
Subject(s) - polarizable continuum model , chemical shift , chemistry , basis set , density functional theory , computational chemistry , solvent effects , polarizability , solvent , basis (linear algebra) , carbon 13 nmr , molecule , mathematics , stereochemistry , organic chemistry , geometry
The main factors affecting the accuracy and computational cost of Gauge‐independent Atomic Orbital – density functional theory (GIAO–DFT) calculation of 15 N NMR chemical shifts in the benchmark series of 16 amides are considered. Among those are the choice of the DFT functional and basis set, solvent effects, internal reference conversion factor and applicability of the locally dense basis set (LDBS) scheme. Solvent effects are treated within the polarizable continuum model (PCM) scheme as well as at supermolecular level with solvent molecules considered in explicit way. The best result is found for Keal and Tozer's KT3 functional used in combination with Jensen's pcS‐3 basis set with taking into account solvent effects within the polarizable continuum model. The proposed LDBS scheme implies pcS‐3 on nitrogen and pc‐2 elsewhere in the molecule. The resulting mean average error for the calculated 15 N NMR chemical shifts is about 6 ppm. The application of the LDBS approach tested in a series of 16 amides results in a dramatic decrease in computational cost (more than an order of magnitude in time scale) with insignificant loss of accuracy.