Coupled-perturbed Hartree-Fock chemical shifts

For the NMR chemical shieldings of four polymers, the chemical shielding tensors were calculated in the coupled perturbed Hartree-Fock (CPHF) method with the gauge-invariant atomic orbital (GIAO) [10], The calculated chemical shift for is defined by... 

Assuming—as it is actually the case — that the determination of the perturbed wave function is the time-limiting step, it is clear that variant (1) is the preferred choice and computationally most efficient. Specifically, there are only three magnetic field components, while there are times this many nuclear magnetic moments. This conclusion holds for Hartree-Fock where the coupled-perturbed HF (CPHF) equations are only solved for B (see, e.g., [35]) as well as the correlated approaches discussed in Section III. We thus conclude that the second derivatives needed for the computation of NMR chemical shifts are best calculated using an asymmetric derivative expression. 

Basis Sets Correlation Consistent Sets Complete Active Space Self-consistent Field (CASSCF) Second-order Perturbation Theory (CASPT2) Configuration Interaction Coupled-cluster Theory Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field G2 Theory Geometry Optimization 1 Gradient Theory Inter-molecular Interactions by Perturbation Theory Molecular Magnetic Properties NMR Chemical Shift Computation Ab Initio NMR Chemical Shift Computation Structural Applications Self-consistent Reaction Field Methods Spin Contamination. 

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