First-Principles Study of Structural and Electronic Properties of Germanene

The ground state structural and electronic properties of germanene (the germanium analogue of graphene) are investigated using first-principles calculations. On structure optimization, the graphene-like honeycomb structure of germanene turns out as buckled (buckling parameter $\Delta = 0.635$ \AA) in contrast with graphene's planar structure (buckling parameter $\Delta = 0.0$ \AA). In spite of this, germanene has similar electronic structure as that of graphene. While corroborating the reported results, we newly predict the in-plane contraction of hexagonal Ge with (thermal) stretching along the "c" axis, akin to a phenomenon observed in graphite.
Comment: Presented in Solid State Physics, Proceedings of the 55th DAE Solid State Physics Symposium 2010, 26-30 December 2010, Manipal, India; Editors: Alka B. Garg, R. Mittal and R. Mukhopadhyay, Bhabha Atomic Research Centre, Mumbai, India; AIP Conference Proceedings 1349, 823-824 (2011). Few typographic errors in the published version corrected; 2pagges, 1 figure