Thermodynamical stability of substoichiometric plutonium monocarbide from first-principles calculations.

Plutonium monocarbide, which contains a considerable amount of vacancies in the carbon sublattice, has never been synthesized in a stoichiometric form. The intriguing substoichiometric behavior of plutonium monocarbide is investigated here using first-principles calculations combined with the special quasirandom structure. It is found that the NaCl-type substoichiometric plutonium monocarbide is stable for PuC0.741-0.923, which is in good agreement with the experiment. From the electronic structure calculations and chemical bond analyses, the stabilization of PuC1-x in this range is attributed to strengthened Pu-C bonds opposite the carbon vacancies.