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Abstract |
By means of a semiempirical analysis the electrostatic energy Eψ of a charge immersed in the screened Coulomb potential of the total charge distribution of the metal was selected as the most appropriate parameter for correlating different cerium environments. The choice was made by determining the smallest dispersion in plots of various physicochemical parameters versus the rate of depression α of the superconducting transition temperature Tc of thorium-based alloys containing cerium impurities. The magnetic moment of cerium, which depends on the environment, was found to have the greatest effect on the depression of Tc. Eψ was found to be proportional to .
The analysis was extended to some ABj compounds (A ≡ elements of groups II–V including cerium and thorium; Bj ≡ N, Sn3, Tl3, Rh3, Co2, Ir2, B6 and Be13). An empirical relationship between Eψ and the volume contraction due to the formation of the compound was found. The cerium valence for any CeBj compound is deduced from the Eψ(Ce) value compatible with the curve of versusEψ(A), taking into account the fact that the valence and atomic radius of cerium are related. |
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