Molecular dynamic simulations of Zr2Ni(1 0 0) surface in presence of Ni or Zr adatoms

We present molecular dynamics simulations results concerning the structural, vibrational and diffusive properties of Zr or Ni adatoms on the Zr2Ni(1 0 0) surface. We found that the (1 0 0) surface is energetically favoured against the (0 0 1) face, while among the various types of terminations, the Zr terminated surfaces were found to be preferred. In addition, we found that there are two available adatom positions for the Ni adatom, while the Zr adatom adopts an equilibrium position that does not correspond to a normal lattice site. Moreover, we found that the Zr is less contracted than the Ni adatom. Interestingly, albeit this stronger contraction, the Ni adatom exhibits larger vibrational amplitudes than Zr, a finding that is closely related to its large diffusivity that takes place via hopping mechanisms which may be much longer than a simple diffusion event and are originated from the availability of the two adatom positions. The diffusion frequency of the Zr adatom is much lower, occurring mainly by simple hopping at higher temperatures. It is worth noting that the diffusion for both adatoms takes place exclusively along the [0 0 1] channel rendering this system appropriate for multiple technological applications that are related with orientational epitaxy and thin film growth.