Isotopic effect at oxygen diffusion in imperfect crystals of cerium oxide

Abstract

The surface and volume diffusion of oxygen isotopes in different phase states of Ce_{1 − x} Gd _x O_{2 − x/2} crystals are studied with the high-speed molecular dynamics method (using graphics processors). It is shown that the ratio between the oxygen isotope diffusion coefficients (the so-called isotopic effect) in the volume of simulated crystals, D(O¹⁶)/D(O¹⁸) ≈ 1.05, agrees well with the well-known ratio $\sqrt {M(O^{18} )/M(O^{16} )} = 1.06$ and does not depend on the temperature, phase state, and particle-particle interaction potential. On the surface of nanocrystals, the isotopic effect is a linear function of temperature. The ratio between diffusion coefficients of light and heavy isotopes grows with decreasing temperature and equals D(O¹⁶)/D(O¹⁸) ≈ 1.12 at T = 1000 K.