High-temperature thermodynamic properties of the UCsub(1 → 2)-phase

The method of expanding the free energy of a solid solution crystal in terms of semi-invariant cumulants as the high-temperature limit is approached has been applied to the UCsub(1 → 2)-phase. The rock-salt-like structure contains linked C-C-pairs in octahedral sites in the f.c.c. Bravais lattice. If there is an attractive interaction of <0.1 eV between adjacent C-C-groups, the cumulant expansion calculations are in good agreement with the measured concentration variation of the partial thermodynamic functions of the system despite the assumption that the pairwise inter-actions are strictly constant. (author)