Spin density, calculation

S. H. Vosko, L. Wilk and M. Nusair, Accurate spin-dependent electron liquid correlation energies for local spin density calculations a critical analysis, Canadian J. Phys., 58,1200 (1980). 

Repeat your analysis fox phenoxy radical. Instead of charge, focus on the spin density. Calculate the delocalization energy using phenoxy radical at phenol geometry. Is it of the same order of magnitude as that for phenoxy anion Explain. 

Vosko, S. J., Wilk, L., Nusair, M., 1980, Accurate Spin-Dependent Electron Liquid Correlation Energies for Local Spin Density Calculations A Critical Analysis , Can. J. Phys., 58, 1200. 

For aromatic hydrocarbon radical anions, this approach works pretty well. Figure 2.7 shows a correlation plot of observed hyperfine splitting versus the spin density calculated from Hiickel MO theory. It also correctly predicts the negative sign of aH for protons attached to n systems. 

The metamagnetic behavior of [Fe(Cp )2] [Ni(a-tpdt)2] is attributed to the AF coupling between the FM coupled D+A D+A chains within the chain layers, as predicted from the application of the McConnell I model and spin density calculations, in a similar way to other salts also based on decamethylmetallocenes and other transition-metal bisdichalcogenate complexes with a type I structural motive such as [Mn(Cp )2][M(tdt)2] (M = Ni, Pd, Pt). 

In diamond, Sahoo et al. (1983) investigated the hyperfine interaction using an unrestricted Hartree-Fock cluster method. The spin density of the muon was calculated as a function of its position in a potential well around the T site. Their value was within 10% of the experimental number. However, the energy profiles and spin densities calculated in this study were later shown to be cluster-size dependent (Estreicher et al., 1985). Estreicher et al., in their Hartree-Fock approach to the study of normal muonium in diamond (1986) and in Si (1987), found an enhancement of the spin density at the impurity over its vacuum value, in contradiction with experiment this overestimation was attributed to the neglect of correlation in the HF method. 

Electron Liquid Correlation Energies for Local Spin Density Calculations A Critical... 

An analysis of the ESR spectrum of the dibenzothiophene radical anion46 yields the following hfs (hyperfine splitting) constants (gffuss) 5.16, 4.48, 1.46, and 0.86. The theoretical values based on HMO data for Model A2 are considerably smaller 2.84, 2.48, 1.47, and 0.27, respectively, which led the authors to make spin-density calculations by the Hartree-Fock method. Quite recently, the spin densities have been calculated for Model B (8S = 1, pcs = 0.566),466 and the following constants were obtained 5.03,3.99,0.75, and — 1.23. A study of the ESR spectrum of the radical derived from 2,8-dimethyl-dibenzothiophene permitted the assignment of the lowest hfe constant value to the proton in position 2. In contrast to the dithiins, experimental data for dibenzothiophene radicals are better reproduced by Model B. 

The spin density calculation, which analyzes the difference between each atom s Mulliken population (see Section 9.1.3.2) of a and ft electrons, indicated the unpaired electron to be highly delocalized, with populations on the ortho and para carbons of the phenyl... 

An MO study of triplet coumarin has indicated that the mobile bond order for the 3,4-double bond decreases significantly on excitation (73MI22201). Furthermore, the electron density at C-3 is decreased but is increased at C-4 and hence an explanation of the orientational specificity of the photoaddition of coumarin to 1,1-diethoxyethylene is available (equation 1) (66TL1419). The reactivity of the 3- and 4-positions of triplet coumarin is also substantiated by the high spin-densities calculated for these positions (70JPC4234). 

This view is been confirmed by an electrochemical product study (Hatta et al. 2001) that is discussed below. The pfCa value of the Thy radical cation has been determined at 3.2 (Geimer and Beckert 1998). When the position at N( ) is substituted by a methyl group and deprotonation of the radical cation can no longer occur at this position, deprotonation occurs at N(3) (Geimer and Beckert 1999 for spin density calculations using density functional theory (DFT) see Naumov et al. 2000). This N(3) type radical is also produced upon biphotonic photoionization of N(l)-substituted Thy anions [reaction (7)] in basic 8 molar NaC104 D20 glasses which allowed to measure their EPR spectra under such conditions (Sevilla 1976). 

Table 1. Calculated HFC constants of corannulene monoanion taken from Ref. [11] and coronene monoanion and spin density calculated using MP2/6-31G(d,p)//lTF/6-31G(d,p)...

The authors also calculated the isotropic hyperfine coupling constants from the spin density at the nucleus. Although RHF spin densities are difficult to compute accurately, the agreement with experiment was reasonable for the boron nucleus, but only half the observed value for fluorine. This is typical of other RHF spin-density calculations (see ref. 176 for details of this work). 

Because spin and s-d transfer energies are equally important in the 3d series, Harris and Jones have carried out numerous calculations for excited states of the 3d atoms, for which detailed spectroscopic data are available, to try to establish the level of accuracy of local spin density calculations of these quantities. These calculations are summarized below and will be used later in interpreting energy curves of the dimers. 

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