Cerium impurity systems

Dederichs PH, Blugel S, Zeller R, Akai H (1984) Ground slates of constrained systems— application to cerium impurities. Phys Rev Lett 53 2512... 

The liquidus and fee to bee transformation data of Vogel and Klose (1954) is the basis for the phase diagram of the lanthanum-eerium system. Their lanthanum was reported to have a purity of 97% (the major impurities were 1.4% Fe, 0.3% eaeh Si and Mg, and 1% miseellaneous) and their eerium a purity of 99.5%. Savitskii and Terekhova (1958) reported data on the liquidus and solidus for this system but did hot include information on the solid state transformations. They claimed a purity of 98.6% for their lanthanum and 97 to 99% for their cerium. Impurity elements were listed but no concentrations were given (Fe and Pr in lanthanum Fe, La, Pr and Nd in cerium). Terekhova (1963) later published a similar phase diagram for this system that seems to be a repetition of that earlier reported by Savitskii and Terekhova. 

The lattice spacing of a 2 at% Er-Ce alloy has been reported by Gschneidner et al. (1962). Information on the purity of their materials is not available. The experimental procedures are summarized in section 2.2.2. Lattice spacings for the erbium-rich portion of the cerium-erbium system have been measured by Norman et al. (1967). Their alloys were made from metals that contained less than lOOppm (by wt ) of other rare earths with approximately 200ppm of the common metals impurities. No information regarding nonmetallic inq>urities was given. 

A phase diagram for the cerium-scandium system has been reported by Naumkin et al. (1964). Distilled scandium of 99.5 (wt )% purity (major impurities 0.2% O, 0.15% Cu, 0.06% Fe, 0.03% N, 0.1% Ti, 0.01% each Al, H, Ca) and 99.5% cerium (major impurities 0.02% each C and Ca and 0.01% each Ta and Fe) were used to prepare the alloys. The alloys were prepared in an arc furnace under helium, remelted three times, then annealed 240hr at 500°C in vacuum. The phase diagram... 

Finally, the column is flushed with three volumes of 0.8 M HC1 to remove sorbed impurities, such as zirconium and plutonium. More precisely, the LiCl eluent solutions are adjusted to within 0.05 M of the desired concentration and are acidified to 0.10 + 0.05 M HC1 hydroxylamine hydrochloride is added (to a concentration of 0.1 M) as a reducing agent for any tetravalent cerium sorbed on the resin and methyl alcohol is added (to a concentration of 2.5% by volume) to suppress the rate of radiolytic destruction of HC1 and the corresponding generation of radiolytic gases (8) Typically, the eluents are added to the feed tank in small portions and pumped to the column thus, the eluents also serve to flush the feed system. The eluent flow rate is 1 L/h and the superficial column velocity is 140 iim/s. 

Many DMFT calculations have been reported in recent years, the majority discussing 3d systems, but also several dealing with actinides. Less attention has been paid to the lanthanides, most probably because the atomic limit, as outlined Section 6.1, is sufficient for an accurate description in most cases. An important exception is the y-cc transition in cerium, which has been the subject of several studies (Held et al., 2001 Zolfl et al., 2001 McMahan et al., 2003 Haule et al., 2005 Amadon et al., 2006), all using the Hubbard model, but with various impurity solvers. Ce compoimds have also been studied based on the Hubbard model (Laegsgaard and Svane, 1998 Sakai et al., 2005 Sakai and Shimuzi, 2007). 

Lundin (1966) studied nine compositions in the cerium-holmium alloy system and reported lattice spacings for four of his alloys. He used 99.9 wt% pure cerium (principal impurities were C, O, Fe, Al, Si, Cu, Mo and W) and 99.9 + wt% pure holmium (principal impurities were O, Zn, Ca and other rare earths) in the preparation of his alloys, which were melted under purified argon in a nonconsumable electrode arc furnace, then homogenized at 650°C for 32 hr followed by rapid cooling. Jayaraman et al. (1966) also reported lattice spacings for a 8 phase... 

Lattice spacing data for the fee cerium-rich portion of this system has been reported by Gsehneidner et al. (1962) and by Harris et al. (1966). Several investigators have reported lattice spacings for the hexagonal portions of this system. No purities were listed by Gsehneidner et al. but the experimental details were given and are summarized in section 2.2.2. Harris et al. (1966) reported that impurities in their... 

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