Hyperfine coupling constants method

Compute the isotropic hyperfine coupling constant for each of the atoms in HNCN with the HF, MP2, MP4(SDQ) and QCISD methods, using the D95(d,p) basis set Make sure that the population analysis for each job uses the proper electron density by including the Density=Current keyword in the route section. Also, include the 5D keyword in each job s route sectionfas was done in the original study). 

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. 

The method presented here for evaluating energy levels from the spin Hamiltonian and then determining the allowed transitions is quite general and can be applied to more complex systems by using the appropriate spin Hamiltonian. Of particular interest in surface studies are molecules for which the g values, as well as the hyperfine coupling constants, are not isotropic. These cases will be discussed in the next two sections. 

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. 

Once a description of the electronic structure has been obtained in these terms, it is possible to proceed with the evaluation of spectroscopic properties. Specifically, the hyperfine coupling constants for oligonuclear systems can be calculated through spin projection of site-specific expectation values. A full derivation of the method has been reported recently (105) and a general outline will only be presented here. For the calculation of the hyperfine coupling constants, the total system of IV transition metal centers is viewed as composed of IV subsystems, each of which is assumed to have definite properties. Here the isotropic hyperfine is considered, but similar considerations apply for the anisotropic hyperfine coupling constants. For the nucleus in subsystem A, it can be... 

Naumov S, Beckert D (2002) Reply to the Comment on A Fourier transform EPR study of uracil and thymine radical anions in aqueous solution)/ by DM Close. Phys Chem Chem Phys 4 45 Naumov S, Barthel A, Reinhold J, Dietz F, Geimer J, Beckert D (2000) Calculation of spin densities of radicals of pyrimidine-type bases by density functional theory. Influence of solvent and comparison with EPR results. Phys Chem Chem Phys 2 4207-4211 Naumov S, Hildenbrand K, von Sonntag C (2001) Tautomers of the N-centered radical generated by reaction of SO4 - with N(1)substituted cytosines in aqueous solution. Calculation of isotropic hyperfine coupling constants by a density functional method. J Chem Soc Perkin Trans 2 1648-1653... 

Pople et al 27) developed the INDO method specifically to account for hyperfine coupling constants in terms of spin densities. Pople, Beveridge and Dobosh have calculated the spin densities of a large number of compounds and found a good agreement with the experimental isotropic hyperfine coupling constants of 1H, 13C, 14N, 170, and 19F (Tables 32 to 35). 

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... 

Table 14 Anisotropic hyperfine coupling constants (in MHz) of H2GN (X2B2). The values of the present work were obtained with the van Duijneveldt AO basis in combination with the MRD-CI/BK method.

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