Generic accommodations of an atom in the Lennard-Jones fcc and hcp rare-gas solids: A computational study

Trapping and thermal migration of the first- and second-row atoms in Ar, Kr and Xe crystals

“…14 Low activation energies of interstitial oxygen and hydrogen were confirmed by several theoretical works, 5,6,12,35,44,46 whereas preferential occupation of the generic interstitial (IS) and single-substitution (SS) sites by light atoms has been demonstrated by the computational studies of the Lennard-Jones models. 49,50 In our recent theoretical analysis of the oxygen TIM, 35 we found that substitutional atoms can be activated by an indirect mechanism that involves point lattice vacancy defects, in full accord with the textbook concept. 51 We also demonstrated the direct processes of SS to SS migration, similar to hypothetical direct and ring mechanisms considered up until the 1950s for cubic metals and alloys.…”

“…It was checked that in these exceptional cases the IS(O h ) sites also exist, but lie a few hundred wavenumbers higher in energy. The SI-related sites were not resolved in the generic searches for the Lennard-Jones interaction model 49,50 and in our previous analysis of the Li@RG and C@Ar systems. 57,83 It should be noted that all of them are strained, lie at high energy and reflect the repulsive branch of the respective A-RG interaction potentials.…”

“…35 and 57 (see also ref. 49 and 50). In a spherical piece of the perfect fcc RG crystal a smaller spherical domain of the mobile atoms is identified.…”

“…It is generic for atoms embedded into the fcc lattice. 49,50 The geometries of the stable sites discussed are attested in the ESI. †…”