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RESEARCH PRODUCT
Why benchmark-quality computations are needed to reproduce 1-adamantyl cation NMR chemical shifts accurately.
Jürgen GaussPaul Von Ragué SchleyerMichael E. Hardingsubject
Quality (physics)Electronic correlationBasis (linear algebra)Computational chemistryChemistryComputationChemical shiftPhysics::Atomic and Molecular ClustersProton NMRPerturbation theory (quantum mechanics)Physical and Theoretical ChemistryCarbon-13 NMRComputational physicsdescription
While the experimental (1)H NMR chemical shiftsof the 1-adamantyl cation can be computed within reasonably small error bounds, the usual Hartree-Fock and density functional quantum-chemical computations, as well as those based on rather elaborate second-order Møller-Plesset perturbation theory, fail to reproduce its experimental (13)C NMR chemical shifts satisfactorily. This also is true even if the NMR shielding calculations treat electron correlation adequately by the coupled-cluster singles and doubles model augmented by a perturbative correction for triple excitations (i.e., at the CCSD(T) level) with quadruple-ζ basis sets. We demonstrate that good agreement can be achieved if highly accurate 1-adamantyl cation equilibrium geometries based on parallel computations of CCSD(T) gradients are employed for the NMR shielding computations.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2011-03-03 | The journal of physical chemistry. A |