Adlayer deposition induced surface crystallization of Cu46Zr54 bulk metallic glass

We present molecular dynamics simulation results on the surface modifications of Cu46Zr54 bulk metallic glass (BMG) that may occur upon deposition of Zr or Cu adlayers. The simulations were based on a semi-empirical potential model in analogy to the tight binding scheme in the second moment approximation. We found that upon Cu adlayer deposition surface alloy is formed that exhibits structuring, while the deposition of Zr adlayer results in the crystalline (1 1 1) closed packed surface. It comes out that in the Cu adlayer case mixed layering with partial structuring occurs at expense of Zr bulk BMG atoms that are fast diffusing to the surface, while in the case of Zr atomic adlayers the mixing is limited close to the interface area and pure element layers crystallize in its energetically favoured face. The effect occurs well below the glass transition temperature and it is visible even at room temperature.