Single-site scatterers

At a different level of approximation, some of the trends for the entire uranium pnictide and chalcogenide series have been studied through single-site scattering phase shifts The number of states is given by... 

Figure 1. Schematic illustration of the CPA theory. Dark sites are occupied by the CPA coherent scat-terer described by the single site scattering matrix tc- The central impurity sites, labelled by A and B, are characterised by the single site matrices Ia and ts.

We imagine an A impurity atom in a otherwise homogeneous crystal with all the other sites occupied by C scatterers. We suppose that the single site scattering matrix of the CPA medium, tc, and its Fermi energy, Ep, have been determined by the CPA theory for the binary alloy The local external field,, takes a constant value within the impurity... 

The dangling bonds of a Si surface abstract one F atom from an incident F2 molecule while the complementary F atom is scattered back into the gas phase [20]. This abstractive mechanism leads to F adsorjDtion at single sites rather than at adjacent pairs of sites, as observed directly by scanning tunnelling microscopy [21]. Br atoms adsorb only to Ga atoms in the second layer of GaAs(001)-(2 x 4) where empty dangling bonds on the Ga atoms can be filled by electrons from the Br atoms [22]. 

Here is the concentration of component a, is the single site t-matrix, Af E) is the scattering path operator and is the matrix element with respect to Xqx-... 

In the single-site approximation, scattering from different sites are taken to be independent, so (6.16) becomes... 

Equation (6.24) is the crucial condition of the CPA, whose physical interpretation is that the scattering from a single site of the effective medium is, on average, the same as that for the exact medium. In view of (6.19), the condition (6.24) reduces to... 

Comparison of model fit variances for cerium indicates a definite superiority of the DFO model over single-site sorption models. The large data scatter in groundwater cerium concentrations, and the ambiguity in extraction inventory trends, indicate that systems producing significant colloidal material may require more specialized models and experimental methods to fully understand their transport mechanisms ... 

The single-site matrix t corresponds to a scattering operator t defined by t yi = iupL for any primitive basis orbital (pi in a given atomic cell. Here Xl = (Pl — fr GoV(pL = Jl Cl<,l From this definition it follows that tJi = v The t-matrix is... 

Solution scattering measurements on half-molecules show that they undergo very similar conformational changes, on iron binding or release, to those of the corresponding lobes of intact transferrins (104). This, together with the structural correspondence noted above, makes them valid as models of single-sited transferrins. The lactoferrin half-... 

The atomic scattering factor applicable to such alloys or solid solutions is an average value, referred to as the site scattering factor, /site. In general, if two atoms, A and B, with atomic scattering factors fA and fB fully occupy a single site in a structure, the site scattering factor is... 

When relativistic spin-orbit coupling effects are omitted, the single-site matrix t 6i) describing the scattering from a site with local moment orientated in the direction ii becomes... 

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