Oxygen Accommodation Below the Top Metal Layer

In principle, oxygen may occupy interstitial or substitutional sites in the crystal, but mostly due to the high cohesive energy of the late TMs, the latter 

Occupation of subsurface sites will commence at a certain total coverage Of, when a structure with a nonzero fraction of the O atoms below the sur- 

Total oxygen coverage (Ml.) Total oxygen coverage (MI.) 

This trend for subsurface accommodation of oxygen atoms at the late 4d TMs can be understood by looking at the subsurface geometries. In all relaxed structures, the subsurface oxygen-metal bond lengths are slightly larger than 

If oxygen penetrates, the deformation cost also rationalizes why subsurface incorporation was found to be more favorable compared to bulk dissolution. 

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