Coupled perturbed Hartree-Fock GIAO method

The particular calculation considered in this tutorial was carried out using the coupled perturbed Hartree-Fock GIAO method with the 6-311G(d,p) basis. Because many of the structures we have studied have unknown experimental geometries, optimized geometries from energy minimization calculations were generally used such is the case in this example. 

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... 

The basic computational method is that of coupled Hartree-Fock perturbation theory (14). At present we prefer the GIAO implementation mentioned above because of its computational efficiency and ease of use, but we have previously used a common gauge-origin method as implemented in the software SYSMO (15) as well as the random-phase approximation, localized orbital (RPA LORG) approach as implemented in the software RPAC (16). 

Another major point in which the theoretical methods differ is the quantum chemical approach to solve the operator equation of the Hamilton operator itself. The most important schemes are Hartree-Fock self consistent field (HF-SCF), density functional theory (DFT) and multi-body second order perturbation theory (MP2). Different combinations have been established, so for instance GIAO-SCF, GlAO-DI I, (,IA()-MI>2, or DF I-IGLO. Most precise measurements on small systems were done with coupled cluster methods, as for instance GIAO-CCSDT-n. ... 

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