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Critical Importance of van der Waals Stabilization in Strongly Chemically Bonded Surfaces: Cu(110):O
We
provide strong evidence that different reconstructed phases
of the oxidized Cu(110) surface are stabilized by the van der Waals
(vdW) interactions. These covalently bonded reconstructed surfaces
feature templates that are an integral part of the surfaces and are
bonded on the bare metal surface by a combination of chemical and
physical bonding. The vdW stabilization in this class of systems affects
predominantly the intertemplate Cu–O interactions in structures
sparsely populated by these templates. The conventional dispersionless
density functional theory (DFT) methods fail to model such systems.
We find a failure to describe the thermodynamics of the different
phases that are formed at different oxygen exposures and spurious
minima on the potential energy surface of a diffusing surface adatom.
To overcome these issues, we employ a range of different DFT methods
that account for the missing vdW correlations. Surprisingly, despite
vast conceptual differences in the different formulations of these
methods, they yield physically identical results for the Cu(110):O
surface phases, provided the massive screening effects in the metal
are taken into account. Contrary, the vibrational contribution does
not consistently stabilize the experimentally observed surface structures.
The van der Waals surface stabilization, so far deemed to play only
a minor role in hard-bonded surfaces, is suggested to be a more general
key feature for this and other related surfaces