Pr pnictides

TABLE 5 Calculated transition pressures for the electronic and structural phase transitions in the Pr pnictides and chalcogenides of Pr, Sm, Eu, Tm, and Yb. Also quoted are the volume discontinuities (relatively to the zero pressure equilibrium volume) at the transition. The notation (f") refers to SIC-LSD calculations with n localized f-electrons. Experimentally, the transitions of SmS are discontinuous, while those of SmSe, SmTe, EuO, EuS, and the Tm and Yb chalcogenides (at room temperature) are continuous. The volume changes for SmSe and SmTe as well as TmTe are obtained by extrapolation over the transition range. For Yb compounds, we quote the relative volumes at which the delocalization starts... 

The SIC-LSD studies on the Pr chalcogenides and pnictides show that the ground state favours the B1 structure over the B2 structure throughout the entire series. With applied pressure, all these compounds undergo a transition to the B2 CsCl structure (or a distorted version of it). For the Pr pnictides, the calculated transition pressures agree quite well with experiment, although they are... 

Fig. 37. Exchange interactions between the ESR probe G

Parks et al. (1984) and Wieliczka et al. (1984b) noticed that the two-peak structure present in cerium systems also appeared in Pr and Nd systems, but the structures there were further removed from Ef. This seems to rule out a Kondo explanation for the upper peak since in that model such a feature is inherently tied to p It is, therefore, of some interest to see whether our approach followed for the Ce compounds would explain the Pr and Nd pnictides in the same manner as it did the Ce pnictides. Comparison will be made with photoemission data on PrSb and NdSb (unfortunately, no resonance data exist). 

The pressure dependence of the low-temperature susceptibility of the Pr and Tm pnictides is rather queer. Based on the point-charge model the crystal-field splitting is expected to increase under pressure and therefore the magnetic susceptibility xcf should decrease but th contrary is observed (Guertin et al., 1975). For TmSb the observed value for 5 In =-1-3 x 10 kbar is nearly... 

---