Multiple-scattering Xa method

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,... 

In the earlier mentioned Multiple-Scattering Xa Method [6], the molecule was geometrically partitioned into three fundamental types of region, Fig. 4 ... 

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

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. 

A basis set may be employed that is of the same form throughout the space of the system, or one in which the orbitals are expanded in different types of basis functions in different parts of space. Such partitioned bases are often used in solid-state calculations in which one must describe an overall wave function that is rapidly varying near the nuclei and slowly varying and free-electron-like when far from the nuclei. Such partitioned bases will be considered further in our discussion of band-theoretical calculations and the multiple-scattering Xa molecular-orbital method. 

Vaughan et al. (1987) propose that the rapid surface oxidation of bor-nite, and the products of this reaction, may result from the surface reconstruction that leads to Cu+ and Fe " being in approximately trigonal planar coordination. Calculations using the multiple-scattering Xa cluster method (MS-SCF-Aa) on Cu+ in tetrahedral and triangular planar coordination with sulfur (on CuS/ and CuSj - clusters see Tossell, 1978b ... 

Ziegler has developed a procedure for analyzing in-complex bond energies within the Density Functional Theory (DFT) formalism [14]. Somewhat confusingly, he labels this the transition-state procedure but this is more in deference to Slater s Multiple Scattering Xa (MSXa) transition-state method [15] (see Sect. 2.5.2) for estimating ionisation and excitation energies and should not be confused with PE surface Transition States. 

Slater s multiple scattering Xa (MS-Xa) around 1970 was a promising quantum chemical method [2], although studies of diatomic molecules and the water molecule clearly showed that the method had shortcomings [3]. These were mainly due to the Muffin-Tin approximation that was used for the molecular potential in particular, the assumption that the molecular potential is constant in the interatomic region. 

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)... 

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