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A molecular dynamics simulation of small PuO2 nanocrystals consisting of 105−174 ions at the temperature T = 1700 K was carried out. The structures of the vertices and the surface created during thermal disordering and subsequent relaxation of these nanocrystals were studied. The vertices formed by two adjacent plutonium cations, as well as truncated vertices of the regular octahedron that consisted of 4 plutonium cations lying in the same plane (100), were most frequently encountered. Sharp vertices of the regular octahedron ending in one cation usually corresponded to metastable states of the crystal lattice or to crystallites with an increased specific energy. According to the results, sequences of the “magic numbers” were proposed to specify the sizes of plutonium dioxide nanocrystals characterized by the most stable surface. [ABSTRACT FROM AUTHOR]

The process of mass transfer in (U,Pu)O2 nanocrystals is studied using the molecular dynamics simulation. The dependence of the vacancy concentration on temperature was estimated by calculating the time of presence of the vacancies in the crystallite bulk. The effective formation energy of vacancies obtained from this dependence was (10 ± 2) eV. Within the limits of error, this energy coincides with the formation energy of the Schottky defect calculated by the lattice static method, and also with the effective energy characterizing the frequency of vacancy formation. [ABSTRACT FROM AUTHOR]