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arXiv · 1303.1924

Spin coupling around a carbon atom vacancy in graphene

M. Casartelli·S. Casolo·G. F. Tantardini·R. Martinazzo
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Abstract

We investigate the details of the electronic structure in the neighborhoods of a carbon atom vacancy in graphene by employing magnetization-constrained density-functional theory on periodic slabs, and spin-exact, multi-reference, second-order perturbation theory on a finite cluster. The picture that emerges is that of two local magnetic moments (one π-like and one σ-like) decoupled from the π- band and coupled to each other. We find that the ground state is a triplet with a planar equilibrium geometry where an apical C atom opposes a pentagonal ring. This state lies ~0.2 eV lower in energy than the open-shell singlet with one spin flipped, which is a bistable system with two equivalent equilibrium lattice configurations (for the apical C atom above or below the lattice plane) and a barrier ~0.1 eV high separating them. Accordingly, a bare carbon-atom vacancy is predicted to be a spin-one paramagnetic species, but spin-half paramagnetism can be accommodated if binding to foreign species, ripples, coupling to a substrate, or doping are taken into account.

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M. Casartelli, S. Casolo, G. F. Tantardini, R. Martinazzo. 2013-03-08. Spin coupling around a carbon atom vacancy in graphene. https://doi.org/10.1103/physrevb.88.195424

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