Iterative extended Hiickel theory

All valence electron (AVE) calculations (simultaneous treatment of O - and 7T-electrons) Three treatments (i) EHT (extended Hiickel theory) (ii) lEHT (iterative extended Hiickel theory) (iii) CNDO treatment (an SCF MO type) 68MI40908 68MI40907 69MI40907... 

In analogy to extended Hiickel theory, there are also charge iterative methods for simple Hiickel theory. The equivalent of eq. (3.90) is... 

Historically, crystal field theory was the first theoretical model (11, 86, 101, 123) used to explain d-d transition energies in metal complexes. Its usefulness is restricted to those complexes whose bonding is largely ionic, and its mqjor deficiency arises from its inability to account for charge transfer transitions. The iterative extended Hiickel and the ab initio, limited basis set, Hartree-Fock calculations are capable of de-... 

The iterative extended Hiickel type of calculation has been widely used, especially by Gray and his co-workers (13) to interpret the visible and ultraviolet spectra of transition metal complexes, but from a quantitative point of view it has not proved to be very reliable. This difficulty arises primarily because the theory is based on a 1-electron Hamiltonian and, therefore, neglects important electron repulsion effects. 

Pure atomic orbitals Extended Htickel theory 40,50) Iterative extended Hiickel theories80 81 82) Quasi SCF diagonal element method85) Kinetic-energy Hiickel theory 58) Zero-differential overlap approximation 61,69) Standard SCF method73 74 75 76,77,78) SCF group function method 83) Random-phase... 

The empirical (semiquantitative) methods are based on a one-electron effective Hamiltonian and may be considered as partly intuitive extended Hiickel theory (EHT) for molecules [204] and its counterpart for periodic systems - the tight-binding (TB) approximation. As, in these methods, the effective Hamiltonian is postulated there is no necessity to make iterative (self-consistent) calculations. Some modifications of the EHT method introduce the self-consistent charge-configuration calculations of the effective Hamiltonian and are known as the method of Mulliken-Rudenberg [209]. 

The values of /3 for each C, were obtained by iteration from the total thermodynamic equilibrium constants based on conductivity measurements. The activity coefficients f2- and / were evaluated from the extended Debye-Hiickel theory. 

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