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13 C carbonyl chemical shielding tensors: Comparing SCF, MBPT (2), and DFT predictions to experiment
Author(s) -
Gonzales Nick,
Simons Jack
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)63:4<875::aid-qua8>3.0.co;2-t
Subject(s) - chemistry , atomic orbital , electromagnetic shielding , tensor (intrinsic definition) , computational chemistry , density functional theory , chemical shift , perturbation theory (quantum mechanics) , shielding effect , electronic correlation , molecular physics , electron , molecule , quantum mechanics , physics , geometry , mathematics , organic chemistry
In this work, we calculate the 13 C nuclear magnetic resonance chemical shielding tensors for 18 carbonyl‐containing compounds. The many‐body perturbation theory (MBPT), self‐consistent field (SCF), and density functional theory (DFT) formalisms were used with gauge including atomic orbitals (GIAO) to calculate the shielding tensors. Our data suggest that shielding tensors can be efficiently estimated by performing one MBPT(2) correlated calculation (e.g., at a reference geometry) and SCF‐level calculations at other geometries and taking the SCF‐to‐correlated tensor element differences to be geometry independent. That is, the correlation contribution to the chemical shielding seems to be relatively constant over a considerable range of distortions. Treatment of correlation using DFT methods is shown to not be as systematically reliable as with MBPT(2). Data on 18 carbonyl compounds show that the single largest influence on the shielding tensor is the presence of nearby electron‐withdrawing or electron‐donating groups. Finally, although good agreement with powder or single‐crystal experimental data is achieved for two or three tensor eigenvalues, systematic differences remain for one element; the origins of these differences are discussed. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 875–894, 1997