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 PuC, which is in good agreement with the experiment. From the electronic structure calculations and chemical bond analyses, the stabilization of PuC in this range is attributed to strengthened Pu-C bonds opposite the carbon vacancies.