['The', 'Morl', ',', 'along', 'with', 'the', 'Grimes', 'shell', 'potential', 'model', ',', 'accurately', 'reproduce', 'the', 'activation', 'energy', 'of', 'oxygen', 'migration', '(', 'the', 'migration', 'path', 'was', 'the', 'lowest', 'energy', 'and', 'most', 'favourable', 'diffusion', 'mechanism', 'observed', 'in', 'bulk', 'UO2', '[', '1', ']', ')', '.']