R-Co systems

Fig. 13.4. Compound formation in the R-Co systems. Notes The following compounds have been claimed to exist but no structural details are available EujCo (Pr, Nd>7Co3 (Gd, Dy, Ho, ErljCo, La Coji (Pr, NdIjCo, (Y, LaljCo,.

Finally, in the R-Ni system the compounds of the type CrB and FeB are observed. These structures can be transformed into each other by changing the stacking sequence (Hohnke and Parthe, 1966). These structures can also be deduced from the cubic close packed structure. Only in the R-Co system are the hexagonally (P63/m) crystallizing R4C03 compounds of the so-called H04C03 type observed (Berthet-Colominas et al., 1968 Lemaire and Schweizer, 1967). In some specific R-Co and many R-Ni systems the orthorhombic structure of the type AhNi is observed. 

Fig. 3, Schematic representation of Intermetallic compounds occurring in R-Co systems. This diagram was constructed from the data listed in Buschow s review (1977a) and the data published by Paithe and Moreau (1977) and van Vucht and Buschow (1976).

It follows that a small periodic perturbation applied to a system, the eigenstates of which are densely distributed in energy, leads to a power dissipation quadratic in the perturbation. For such a linear system it is possible to define an impedance Z(co), the ratio of the force V to the response Q, where all quantities are now assumed to be in standard complex notation, V = Z(u>)Q. The instantaneous power is VQR u )/ Z oj), where R(co), the resistance, is the real part of Z(lu). 

In the limit co J. 0 the radius R(co) becomes infinite and both potentials differ by a constant A everywhere. We will now show that A is unequal to zero. If we now insert v dN to) = o (JV) + A in the Kohn-Sham equations for the N -1- co-particle system and use the fact that for small to the orbitals in the region... 

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