Displacement energy of the surface layers of tungsten

A molecular dynamics study with BOP potential is used to calculate the threshold displacement energy (E$_{\mathrm{D}})$ of primary knock-on atoms in the surface layers of the tungsten bcc crystal lattice at 300 K and at various crystallographic directions. Depending on the direction, E$_{\mathrm{D}}$ is 10{\%} to 75{\%} smaller from the bulk value at the first layer, interfacing vacuum, while it reaches close to the bulk value already at the third tungsten layer.