  We show for the first time that highly localized in-plane breathers can
propagate in specific directions with minimal lateral spreading in a model 2-D
hexagonal non-linear lattice. The lattice is subject to an on-site potential in
addition to longitudinal nonlinear inter-particle interactions. This study
investigates the prediction that stable breather-like solitons could be formed
as a result of energetic scattering events in a given layered crystal and would
propagate in atomic-chain directions in certain atomic planes. This prediction
arose from a long-term study of previously unexplained dark lines in natural
crystals of muscovite mica.
