Ab initio NMR parameters of BrCH3 and ICH3 with relativistic and vibrational corrections

This study is focused on two effects identified when NMR parameters are calculated based on first principles. These effects are 1. vibrational correction of properties when using ab initio optimized equilibrium geometry; 2. relativistic effects and limits of using the Flygare equation. These effects...

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Bibliographic Details
Published in:Molecular physics 2018-05, Vol.116 (9), p.1192
Main Authors: Uhlíková, Tereza, Urban, S, te, pán
Format: Article
Language:English
Subjects:
First principles
Mathematical analysis
NMR
Nuclear magnetic resonance
Nuclear spin
Parameter identification
Relativism
Relativistic effects
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Summary:This study is focused on two effects identified when NMR parameters are calculated based on first principles. These effects are 1. vibrational correction of properties when using ab initio optimized equilibrium geometry; 2. relativistic effects and limits of using the Flygare equation. These effects have been investigated and determined for nuclear spin-rotation constants and nuclear magnetic shieldings for the CH3Br and CH3I molecules. The most significant result is the difference between chemical shieldings determined based on the ab initio relativistic four-component Dirac-Coulomb Hamiltonian and chemical shieldings calculated using experimental values and the Flygare equation. This difference is approximately 320 ppm and 1290 ppm for 79Br and 127I in the CH3X molecule, respectively.
ISSN:0026-8976
1362-3028
DOI:10.1080/00268976.2017.1416194