Uranium monopnictides

Fig. 17. Ordered magnetic moments and ordering temperatures of uranium monopnictides and monochalcogenides as a function of the lattice constant The U-U separation is simply tZ(,/ /5. The ordering temperatures are indicated by the right-hand scale and marked as solid circles. The values of the ordered moments are indicated by the left-hand scale and marked with solid squares. (From Buyers and Holden 1985.) Note that this figure appeared also in many earlier works.

I. UN, UP, UAs, USb, UBi. Since the uranium monopnictides and mono-chalcogenides are the only actinide compounds of which samples are readily available, and since they can be handled without any special precautions, they have been explored in much detail over the past 40 years. The first summary of the present state of knowledge is a survey up to the year 1970 by Kuznietz (1971). A more extended publication by Lam and Aldred (1974) carefully collects all the results up to 1972. A later summary given by Lander (1978) covers data up to 1977. The following discussion concentrates on the more recent results. 

Fig. 56. The measured (filled triangles and circles) and calculated (indicated by full line) lattice constants of the uranium mono-chalcogenides and monopnictides.

Fig. 57. The calculated bulk moduli (open squares) of the uranium monochalcogenides (right) and monopnictides (left) compared with measurements. The open circles indicate data from measurements by Holden et al. (1982), Vedel et al. (1986), Neuenschwander et al. (1984), Buyers et al. (1983), Jackman et al. (1986), Olsen et al. (1984) and DuPlessis et al. (1985) for the chalcogenides and from Guinan and Cline (1972), Padel et al. (1970), Van Doom and DuPlessis (1977), Fournier et al. (1980), Leger et al. (1986, 1988), Stirling et al. (1983) and Neuenschwander et al. (1986) for the pnictides. More details of the measurements are given by Gerward et al. (1989) and Olsen et al. (1989), from which the filled-circle data points are taken.

Reason (b), which was the driving scientific reason for studying these systems is now recognized to be much more complex. Divalent uranium or other actinide species are almost impossible to stabilize, and so are not expected. Numerous studies, see the reviews byS choenes (1984), Brooks et al. (1984), and Baer (1984), have shown that all the monopnictides and monochalcogenides (and thus all the solid solutions as well) are essentially semimetals. It is generally accepted that the monopnictides are... 

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