Xa multiple scattering

The Xa multiple scattering method generates approximate singledeterminant wavefunctions, in which the non-local exchange interaction of the Hartree-Fock method has been replaced by a local term, as in the Thomas-Fermi-Dirac model. The orbitals are solutions of the one-electron differential equation (in atomic units)... 

The self-consistent statistical exchange (Xa) multiple scattered wave method, which is well described in Ref. (58), has also been used by Bair a and Robaux (59) to assign the peaks in the UP-spectrum of CO/Ni. 

Case, D. A., and M. Karplus (1976). The calculation of one-electron properties from Xa multiple scattering wavefunctions. Chem. Phys. Lett. 39, 33-38. 

There have been few first principles calculations for ions and no form factor calculations. Brown and Burton s spin-unrestricted Hartree-Fock SCFMO calculations (93) for K2NaCrFegave /< = -2.19%, f =2.SS% and/<,-/ = -4.74%, in quite good agreement with the experimental estimates (Table 4), but a somewhat small value of fa — fn —6.5%) was estimated for MnFe"" (cf. Table 5). On the other hand the Xa multiple scattering calculation of Larsson and Connolly (94) indicates that the contribution to /<, — f from Cg spin polarization is dominant... 

In the framework of the Xa-multiple scattering theory, the absorption cross section is determined by the multiple scattering matrix M of the photoelectron with kinetic... 

Angular information is notably absent from the list of structural parameters normally obtained from XAS. One approach to obtaining angular detail is to make use of multiple scattering effects (17). Unfortunately, this technique is only useful for outer shells (non-nearest neighbor atoms) where there are atoms intervening between the absorber and the scatterer. This technique suffers from complications if the shells of interest overlap in distance with other shells of atoms. 

Multiple scattering Xa (MSXa) method was applied to assign the optical absorption spectra of Me3Si and (MeS)3Si radicals. The strong band... 

Fig. 1. X-ray absorption spectrum (XAS) of Cu—Zn metallothionein at the Cu and Zn K-edges. The structure near the edge, referred to as XANES is dominated by multiple scattering events while the extended structure, referred to as EXAFS, at photoelectron energies greater than 30-50 eV is primarily due to single scattering events...

The SCF-Xa Scattered-wave Method.—An alternative to the LCAO-MO method for molecules is the Xa scattered wave or multiple-scattering Xa method, which was suggested less than 10 years ago114 and now has an extensive literative. The basic theory has been refined in several directions115 and there are several excellent reviews.116-180 The method is based on the scattered-wave method in solids181 and aims to solve the Fock equation,... 

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