A theoretical study of the energies of formation of point defects in CaF₂and UO₂

Comparison of interatomic potentials for UO2

“…The increase of mobility above %2300-2600 K was often reported in previous simulations of UO 2 [4,13,18,12], our results confirm the observations of Walker [4] and Lindan and Gillan [18] that despite their mobility, oxygen atoms remain ordered.…”

“…Two models accounting for atomic description have been considered by the different authors having developed potentials for UO 2 [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The first one is the rigid ion model, which describes atoms as massive point charges interacting by electrostatic interactions and a short-range potential.…”

Comparison of interatomic potentials for UO2. Part I: Static calculations

“…The first available sets of parameters for the UO 2 systems, developed by Tharmalingam [4], were fitted on elastic properties, and used in order to calculate point defect energies. The calculations were done using the point polarizable ion model, which according to Catlow and Norgett [5], can show instabilities in the calculation of dipoles interaction.…”

Point Defect Parameters for Calcium Fluoride From Ionic Conductivity Measurements at Low Temperatures

“…Les donnees ont kt6 analysks a l'aide de techniques des moindres carres non lineaires pour obtenir des valeurs numeriques des paramktres gouvernant la formation et la migration des dkfauts. Ces resultats sont comparQ avec des travaux experimentaux et theoriques anttrieurs, et montrent que la valeur probable de l'bnergie de formation des defauts de Frenkel dans le sous-reseau d'anions est 2,7 eV et que les energies de migration des lacunes et des interstitiels anioniques se situent respectivement dans les intervalles 0,35-0,55 eV et 0,78-0,92 eV.…”

“…impurity on the cation sub-lattice = c, f c,, ; and z, is the number of anion sites that are nn to a cation site = 8 in the fluorite lattice. Note the use of site fractions in (2). If mole fractions x, are used a factor 2 appears on the RS of (2) since x, = 2 cv.…”