Calculation of Hyperfine Coupling Constants

Barone also introduces two new basis sets, EPR-Il and EPR-llI. These are optimized for the calculation of hyperfine coupling constants by density functional methods. EPR-Il is a double zeta basis set with a single set of polarization functions and an enhanced s part. EPR-III is a triple zeta set including diffuse functions, double d polarization functions and a single set off functions. 

We have also performed the calculation of hyperfine coupling constants the electric quadrupole constant B and magnetic dipole constant A, with inclusion of nuclear finiteness and the Uehling potential for Li-like ions. Analogous calculations of the constant A for ns states of hydrogen-, lithium- and sodiumlike ions were made in refs [11, 22]. In those papers other bases were used for the relativistic orbitals, another model was adopted for the charge distribution in the nuclei, and another method of numerical calculation was used for the Uehling potential. 

Some the best-known work of Grein and his coworkers involves the development of methods for the calculation of hyperfine coupling constants.141 More recently the focus has shifted to calculating magnetic g-tensors from highly correlated wavefunctions. Grein s current interests include the study of stereoelectronic effects (such as the anomeric and reverse anomeric effects in acetal-like systems) in organic chemistry, a topic to which he has made important contributions.142... 

Even more complex ESR spectra can occur for nitrogen-containing aromatic radicals of the type in Fig. 3.4. A stickplot analysis is not easily performed. At this level of complexity a combination of ESR and ENDOR measurements, simulation of the observed spectra, and theoretical calculations of hyperfine coupling constants is often applied to obtain a reliable assignment. The procedure to obtain the coupling constants from the ENDOR spectrum of the Wurster blue cation is indicated in Exercise E3.3. ENDOR lines due to can be observed more easily than signals due to " N, a phenomenon that is quite typical in CW-ENDOR studies. The hyperfine couplings due to N nuclei may therefore have to be deduced from simulation of the ESR spectrum. 

NMR measurements at 310 MHz variable temperature study enthalpy difference between conformational states INDO calculation of hyperfine coupling constants. 

From [71Janl]. MO calculation of hyperfine coupling constants INDO-UHF method. ... 

Calculation of hyperfine coupling constants using Lutz and Barfield equations. 

In general, the most severe basis set requirements come from the isotropic hyperfine interactions, the anisotropic contribution in general being well converged with basis sets that perform well for the isotropic contribution. We mention in particular that there are basis sets specifically designed for calculations of hyperfine coupling constants (EPR-III) using density functional... 

Even though the majority of calculations of hyperfine coupling constants are performed using unrestricted approaches, the importance of spin contamination and its effect on the hyperfine coupling constants remains somewhat unclear, in particular in DFT calculations. Whereas restricted and unrestricted approaches give more or less identical results for simple radicals, the situation is less clear in the case of transition metal compounds, and a few examples of the differences between restricted and unrestricted approaches are collected in O Table 11-15, based on the results reported by Rinkevicius et al. (2004). We note that the differences between restricted and unrestricted approaches in general are small for the same functional, but that these differences become significant when spin contamination can be a problem, for instance for TiFs and MnOs. 

Multiconfiguration self-consistent-field calculations of hyperfine coupling constants. Journal of Chemical Physics, 97, 3412. 

Engels B, Peyerimhoff SD, Davidson ER (1987) Calculation of hyperfine coupling-constants -an ab initio MRD Cl study for nitrogen to analyze the effects of basis-sets and Cl parameters. Mol Phys 62 109-127... 

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