  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.

Mesoscale and Nanoscale Physics;Materials Science