Complex structure due to As bonding and interplay with electronic structure in superconducting BaNi2As2

BaNi2As2 is a superconductor chemically related to the Fe-based superconductors, with a complex and poorly understood structural phase transition. We show based on first principles calculations that in fact there are two distinct competing structures. These structures are very different from electronic, transport and bonding points of view but are close in energy. These arise due to complex As bonding patterns and drive distortions of the Ni layers. This is supported by photoemission experiments. This leads to an interplay of electronic and structural behavior including induced anisotropic of the electronic transport. The competition between these distortions is associated with the complex behavior observed in BaNi2As2 samples.