Bulk intermediate-valence compounds

For the intermediate-valence compound YbCuAl, MacLaughlin et al. (1979) observed a linear relationship between and x only for temperatures above the maximum of the bulk susceptibility. For T < == 27 K, this relation was no... 

The very same charge deformability of the mixed-valence Sm ion due to 4f" - 4f"5d excitations used for the description of the Raman intensities in fig. 37 has been used to describe the phonon anomalies (Bilz et al. 1979). Therefore we can conclude that the dominant F scattering intensities of Sm 25S near 250 cm" and 85 cm , respectively, arise mainly from the LO and LA phonon anomalies in the [111] direction, emphasizing scattering from L-point phonons. The available data on the LO(L) phonon frequencies of RS are depicted in fig. 38 as a function of the lattice parameter. The LO(L) phonons of intermediate-valence metallic SmS and Sm jY 25S lie between the divalent reference line given by YbS and EuS, and the trivalent reference line spanned by YS, GdS, PrS and LaS, thus exhibiting the behavior of an alloy of divalent and trivalent Sm ions. Figure 39 shows the bulk modulus of several RS compounds at room... 

The activity of E(0) is regarded to be 1 (solid pure metal). Fmther, the concentration Cn of the high-valence compound E(N) at the surface of the cathode and in the bulk is assumed to be equal. This is acceptable for not very dilute solutions. We can now express the cathodic surface concentration of the intermediate by... 

The majority of crystals can be classified as semi-ionic (with chemical bonding being intermediate between covalent and purely ionic limits). For such crystals the adequacy of selected basis sets must be carefully tested as is discussed in [458], for example, for semi-ionic compounds Si02 (quartz) and AI2O3 (corundum). The exponents of the outer shell for the two cations (Si and Al) used in molecular calculations prove to be too diffuse. For the Si atom in quartz, reoptimization in the bulk gives a = 0.15 (instead of the molecular value 0.09). Corundum is more ionic than quartz, and in this case it is better to eliminate the most diffuse valence shell of Al, and to use two Gaussians of the inner valence shells as independent functions (a = 0.94 and a = 0.3, respectively). 

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